METHOD AND SYSTEM FOR PRINTING ALIGNED NANOWIRES AND OTHER ELECTRICAL DEVICES
Methods and systems for applying nanowires and electrical devices to surfaces are described. In a first aspect, at least one nanowire is provided proximate to an electrode pair. An electric field is generated by electrodes of the electrode pair to associate the at least one nanowire with the electrodes. The electrode pair is aligned with a region of the destination surface. The at least one nanowire is deposited from the electrode pair to the region. In another aspect, a plurality of electrical devices is provided proximate to an electrode pair. An electric field is generated by electrodes of the electrode pair to associate an electrical device of the plurality of electrical devices with the electrodes. The electrode pair is aligned with a region of the destination surface. The electrical device is deposited from the electrode pair to the region.
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This application is a divisional of allowed U.S. application Ser. No. 12/114,446, filed on May 2, 2008, which claims the benefit of U.S. Provisional Application No. 60/916,337, filed on May 7, 2007, both of which are incorporated by reference herein in their entireties.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to nanostructures, and more particularly, to the deposition of aligned nanostructures and electrical devices.
2. Background of the Invention
Nanostructures, such as nanowires, have the potential to facilitate a whole new generation of electronic devices. A major impediment to the emergence of this new generation of electronic devices based on nanostructures is the ability to effectively align and deposit the nanostructures on various surfaces, such as substrates. Electric fields enable the alignment of nanowires suspended in suspension, but current techniques pose stringent constraints on the scalability to large area substrates. Likewise, current techniques for depositing electrical devices, such as integrated circuits, dies, optical components, etc., do not scale well to large area substrates.
What are needed are systems and methods for achieving a high quality deposition of nanostructures and other electrical devices that are suitable for manufacturing large arrays of nanostructure-enabled electronic devices.
SUMMARY OF THE INVENTIONMethods and systems for applying nanowires to surfaces are described. In an example aspect, nanowires are provided proximate to an electrode pair. An electric field is generated by electrodes of the electrode pair to associate the nanowires with the electrodes. The electrode pair is aligned with a region of the destination surface. The nanowires are deposited from the electrode pair to the region.
The nanowires may be deposited to the region in a variety of ways. For example, a passive or active force, or combination of such forces, may be used to move the nanowires from the electrodes to the destination surface. Example forces include an electric field (AC and/or DC), a vacuum force, an electrostatic force, gravity, and/or other forces.
In a first example, the electrode pair may be formed on a transfer surface. The transfer surface is configured to have a first electric charge. The first electric charge applies a repulsive electrostatic force to the nanowires (e.g., the nanowires may have the same charge as the first electric charge). The electric field generated by the electrodes attracts the nanowires to the transfer surface against the repulsive electrostatic force. In one instance, the electric field may be biased with an alternating current (AC) field to attract the nanowires to the transfer surface. The electric field may be reduced (including entirely removed) to enable the nanowires to be moved toward the destination surface by the repulsive electrostatic force of the first electric charge.
In another example, the destination surface has a second electric charge that is opposite the first electric charge. An attractive electrostatic force of the second electric charge attracts the nanowires to the destination surface. A distance between the nanowires and the destination surface may be reduced to increase this attraction.
In another example, the transfer surface is vibrated (e.g., ultrasonically) to enable the attractive electrostatic force of the second electric charge to attract the nanowires toward the destination surface.
In another example, a vacuum is applied from the destination surface to the transfer surface to move the nanowires toward the destination surface. For example, the vacuum may draw a solution in which the nanowires reside towards the destination surface. The solution flow draws the nanowires toward the destination surface.
In another example, a second electric field associated with the destination surface is generated to attract the nanowires toward the destination surface.
In another aspect of the present invention, a system for applying nanowires to a destination surface is described. The system includes a body having a transfer surface, an electrode pair formed on the transfer surface, a suspension that includes a plurality of nanowires provided proximate to the electrode pair, a signal generator, and an alignment mechanism. The signal generator is coupled to the electrode pair. The signal generator is configured to supply an electric signal to enable electrodes of the electrode pair to generate an electric field to associate nanowires of the plurality of nanowires with the electrodes. The alignment mechanism is configured to align the electrode pair with a region of the destination surface to enable the nanowires to be deposited from the electrode pair to the region.
In another aspect of the present invention, electrical devices are transferred to surfaces in a similar manner as described elsewhere herein for nanowires. In aspects, one or more electrical devices are provided proximate to an electrode pair on a transfer surface. The electrode pair is energized, whereby an electrical device becomes associated with the electrode pair. Subsequently, the electrical device is deposited from the electrode pair to a destination surface.
In another aspect of the present invention, nanostructures, such as nanowires, are transferred to a destination surface. A transfer surface of a print head is positioned adjacent to a destination surface. A nanowire is associated with the transfer surface. A distance between the transfer surface and the destination surface is reduced. A fluid is received in one or more openings in the transfer surface from between the transfer surface and the destination surface during the reducing of the distance between the transfer and destination surfaces. Receiving the fluid in the opening(s) reduces a shear force on the nanowire. The nanowire is deposited from the transfer surface to the destination surface.
In still another aspect of the present invention, nanostructures, such as nanowires, are transferred to a destination substrate. A nanowire transfer system includes an association station, a printing station, and a cleaning station. The association station is configured to receive a plurality of print heads, and to associate nanostructures with a transfer surface of each of the received plurality of print heads. The printing station is configured to receive a destination substrate and at least one of the print heads, and to transfer the nanostructures from the received print head(s) to a plurality of regions of a surface of the destination substrate. The cleaning station is configured to receive the plurality of print heads from the printing station, and to clean the received plurality of print heads.
In aspects, the printing station may be configured to perform the transfer of the nanostructures as a “wet” transfer or a “dry” transfer.
In a further aspect, the nanowire transfer system may include an inspection station. The inspection station is configured to perform an inspection of the transfer surfaces of the plurality of print heads, and to select at least one print head of the plurality of print heads based on the inspection. The printing station may be configured to transfer the nanostructures from the selected at least one print head.
In a still further aspect, the nanowire transfer system may include a repair station. The repair station is configured to perform an inspection of the nanostructures transferred to the plurality of regions of the surface of the destination substrate. If the repair station determines an arrangement of nanostructures in need of repair, the repair station is configured to repair the arrangement of nanostructures.
In a still further aspect, the nanowire transfer system may include a print head drying station and a repair station. The print head drying station is configured to dry the nanostructures associated with the transfer surfaces of the plurality of print heads. The repair station is configured to perform an inspection of the dried transfer surfaces. If the repair station determines an arrangement of nanostructures associated with a transfer surface in need of repair, the repair station is configured to repair the determined arrangement of nanostructures. The print head drying station enables a dry transfer of the nanowires to be performed at the printing station.
In a still further aspect, the nanowire transfer system may include a panel drying station. The panel drying station is configured to dry the nanostructures transferred to the plurality of regions of the surface of the destination substrate (e.g., if a wet transfer of the nanowires is performed by the printing station)
Further embodiments, features, and advantages of the invention, as well as the structure and operation of the various embodiments of the invention are described in detail below with reference to accompanying drawings.
The invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawing in which an element first appears is indicated by the left-most digit in the corresponding reference number.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.
DETAILED DESCRIPTION OF THE INVENTIONIt should be appreciated that the particular implementations shown and described herein are examples of the invention and are not intended to otherwise limit the scope of the present invention in any way. Indeed, for the sake of brevity, conventional electronics, manufacturing, semiconductor devices, and nanowire (NW), nanorod, nanotube, and nanoribbon technologies and other functional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail herein. Furthermore, for purposes of brevity, the invention is frequently described herein as pertaining to nanowires.
It should be appreciated that although nanowires are frequently referred to, the techniques described herein are also applicable to other nanostructures, such as nanorods, nanotubes, nanotetrapods, nanoribbons and/or combinations thereof. It should further be appreciated that the manufacturing techniques described herein could be used to create any semiconductor device type, and other electronic component types. Further, the techniques would be suitable for application in electrical systems, optical systems, consumer electronics, industrial electronics, wireless systems, space applications, or any other application.
As used herein, an “aspect ratio” is the length of a first axis of a nanostructure divided by the average of the lengths of the second and third axes of the nanostructure, where the second and third axes are the two axes whose lengths are most nearly equal to each other. For example, the aspect ratio for a perfect rod would be the length of its long axis divided by the diameter of a cross-section perpendicular to (normal to) the long axis.
The term “heterostructure” when used with reference to nanostructures refers to nanostructures characterized by at least two different and/or distinguishable material types. Typically, one region of the nanostructure comprises a first material type, while a second region of the nanostructure comprises a second material type. In certain embodiments, the nanostructure comprises a core of a first material and at least one shell of a second (or third etc.) material, where the different material types are distributed radially about the long axis of a nanowire, a long axis of an arm of a branched nanocrystal, or the center of a nanocrystal, for example. A shell need not completely cover the adjacent materials to be considered a shell or for the nanostructure to be considered a heterostructure. For example, a nanocrystal characterized by a core of one material covered with small islands of a second material is a heterostructure. In other embodiments, the different material types are distributed at different locations within the nanostructure. For example, material types can be distributed along the major (long) axis of a nanowire or along a long axis of arm of a branched nanocrystal. Different regions within a heterostructure can comprise entirely different materials, or the different regions can comprise a base material.
As used herein, a “nanostructure” is a structure having at least one region or characteristic dimension with a dimension of less than about 500 nm, e.g., less than about 200 nm, less than about 100 nm, less than about 50 nm, or even less than about 20 nm. Typically, the region or characteristic dimension will be along the smallest axis of the structure. Examples of such structures include nanowires, nanorods, nanotubes, branched nanocrystals, nanotetrapods, tripods, bipods, nanocrystals, nanodots, quantum dots, nanoparticles, branched tetrapods (e.g., inorganic dendrimers), and the like. Nanostructures can be substantially homogeneous in material properties, or in certain embodiments can be heterogeneous (e.g., heterostructures). Nanostructures can be, for example, substantially crystalline, substantially monocrystalline, polycrystalline, amorphous, or a combination thereof. In one aspect, each of the three dimensions of the nanostructure has a dimension of less than about 500 nm, for example, less than about 200 nm, less than about 100 nm, less than about 50 nm, or even less than about 20 nm.
As used herein, the term “nanowire” generally refers to any elongated conductive or semiconductive material (or other material described herein) that includes at least one cross-sectional dimension that is less than 500 nm, and preferably, equal to or less than less than about 100 nm, and has an aspect ratio (length:width) of greater than 10, preferably greater than 50, and more preferably, greater than 100. Exemplary nanowires for use in the practice of the methods and systems of the present invention are on the order of 10's of microns long (e.g., about 10, 20, 30, 40, 50 microns, etc.) and about 100 nm in diameter.
The nanowires of this invention can be substantially homogeneous in material properties, or in certain embodiments can be heterogeneous (e.g., nanowire heterostructures). The nanowires can be fabricated from essentially any convenient material or materials, and can be, e.g., substantially crystalline, substantially monocrystalline, polycrystalline, or amorphous. Nanowires can have a variable diameter or can have a substantially uniform diameter, that is, a diameter that shows a variance less than about 20% (e.g., less than about 10%, less than about 5%, or less than about 1%) over the region of greatest variability and over a linear dimension of at least 5 nm (e.g., at least 10 nm, at least 20 nm, or at least 50 nm). Typically the diameter is evaluated away from the ends of the nanowire (e.g., over the central 20%, 40%, 50%, or 80% of the nanowire). A nanowire can be straight or can be e.g., curved or bent, over the entire length of its long axis or a portion thereof. In certain embodiments, a nanowire or a portion thereof can exhibit two- or three-dimensional quantum confinement. Nanowires according to this invention can expressly exclude carbon nanotubes, and, in certain embodiments, exclude “whiskers” or “nanowhiskers”, particularly whiskers having a diameter greater than 100 nm, or greater than about 200 nm.
Examples of such nanowires include semiconductor nanowires as described in Published International Patent Application Nos. WO 02/17362, WO 02/48701, and WO 01/03208, carbon nanotubes, and other elongated conductive or semiconductive structures of like dimensions, which are incorporated herein by reference.
As used herein, the term “nanorod” generally refers to any elongated conductive or semiconductive material (or other material described herein) similar to a nanowire, but having an aspect ratio (length:width) less than that of a nanowire. Note that two or more nanorods can be coupled together along their longitudinal axis so that the coupled nanorods span all the way between electrodes. Alternatively, two or more nanorods can be substantially aligned along their longitudinal axis, but not coupled together, such that a small gap exists between the ends of the two or more nanorods. In this case, electrons can flow from one nanorod to another by hopping from one nanorod to another to traverse the small gap. The two or more nanorods can be substantially aligned, such that they form a path by which electrons can travel between electrodes.
A wide range of types of materials for nanowires, nanorods, nanotubes and nanoribbons can be used, including semiconductor material selected from, e.g., Si, Ge, Sn, Se, Te, B, C (including diamond), P, B—C, B—P(BP6), B—Si, Si—C, Si—Ge, Si—Sn and Ge—Sn, SiC, BN, BP, BAs, MN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, Cul, AgF, AgCl, AgBr, Agl, BeSiN2, CaCN2, ZnGeP2, CdSnAs2, ZnSnSb2, CuGeP3, CuSi2P3, (Cu, Ag)(Al, Ga, In, Tl, Fe)(S, Se, Te)2, Si3N4, Ge3N4, Al2O3, (Al, Ga, In)2 (S, Se, Te)3, Al2CO, and an appropriate combination of two or more such semiconductors.
The nanowires can also be formed from other materials such as metals such as gold, nickel, palladium, iradium, cobalt, chromium, aluminum, titanium, tin and the like, metal alloys, polymers, conductive polymers, ceramics, and/or combinations thereof. Other now known or later developed conducting or semiconductor materials can be employed.
In certain aspects, the semiconductor may comprise a dopant from a group consisting of: a p-type dopant from Group III of the periodic table; an n-type dopant from Group V of the periodic table; a p-type dopant selected from a group consisting of: B, Al and In; an n-type dopant selected from a group consisting of: P, As and Sb; a p-type dopant from Group II of the periodic table; a p-type dopant selected from a group consisting of: Mg, Zn, Cd and Hg; a p-type dopant from Group IV of the periodic table; a p-type dopant selected from a group consisting of: C and Si; or an n-type dopant selected from a group consisting of: Si, Ge, Sn, S, Se and Te. Other now known or later developed dopant materials can be employed.
Additionally, the nanowires or nanoribbons can include carbon nanotubes, or nanotubes formed of conductive or semiconductive organic polymer materials, (e.g., pentacene, and transition metal oxides).
Hence, although the term “nanowire” is referred to throughout the description herein for illustrative purposes, it is intended that the description herein also encompass the use of nanotubes (e.g., nanowire-like structures having a hollow tube formed axially therethrough). Nanotubes can be formed in combinations/thin films of nanotubes as is described herein for nanowires, alone or in combination with nanowires, to provide the properties and advantages described herein.
It should be understood that the spatial descriptions (e.g., “above”, “below”, “up”, “down”, “top”, “bottom,” “vertical,” “horizontal,” etc.) made herein are for purposes of illustration only, and that devices of the present invention can be spatially arranged in any orientation or manner.
The valence band of the insulating shell can be lower than the valence band of the core for p-type doped wires, or the conduction band of the shell can be higher than the core for n-type doped wires. Generally, the core nanostructure can be made from any metallic or semiconductor material, and the one or more shell layers deposited on the core can be made from the same or a different material. For example, the first core material can comprise a first semiconductor selected from the group consisting of: a Group II-VI semiconductor, a Group III-V semiconductor, a Group IV semiconductor, and an alloy thereof. Similarly, the second material of the one or more shell layers can comprise an oxide layer, a second semiconductor, the same as or different from the first semiconductor, e.g., selected from the group consisting of: a Group II-VI semiconductor, a Group III-V semiconductor, a Group IV semiconductor, and an alloy thereof. Example semiconductors include, but are not limited to, CdSe, CdTe, InP, InAs, CdS, ZnS, ZnSe, ZnTe, HgTe, GaN, GaP, GaAs, GaSb, InSb, Si, Ge, AlAs, AlSb, PbSe, PbS, and PbTe. As noted above, metallic materials such as gold, chromium, tin, nickel, aluminum etc. and alloys thereof can be used as the core material, and the metallic core can be overcoated with an appropriate shell material such as silicon dioxide or other insulating materials, which may in turn may be coated with one or more additional shell layers of the materials described above to form more complex core-shell-shell nanowire structures.
Nanostructures can be fabricated and their size can be controlled by any of a number of convenient methods that can be adapted to different materials. For example, synthesis of nanocrystals of various composition is described in, e.g., Peng et al. (2000) “Shape Control of CdSe Nanocrystals” Nature 404, 59-61; Puntes et al. (2001) “Colloidal nanocrystal shape and size control: The case of cobalt” Science 291, 2115-2117; U.S. Pat. No. 6,306,736 to Alivisatos et al. (Oct. 23, 2001) entitled “Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process”; U.S. Pat. No. 6,225,198 to Alivisatos et al. (May 1, 2001) entitled “Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process”; U.S. Pat. No. 5,505,928 to Alivisatos et al. (Apr. 9, 1996) entitled “Preparation of III-V semiconductor nanocrystals”; U.S. Pat. No. 5,751,018 to Alivisatos et al. (May 12, 1998) entitled “Semiconductor nanocrystals covalently bound to solid inorganic surfaces using self-assembled monolayers”; U.S. Pat. No. 6,048,616 to Gallagher et al. (Apr. 11, 2000) entitled “Encapsulated quantum sized doped semiconductor particles and method of manufacturing same”; and U.S. Pat. No. 5,990,479 to Weiss et al. (Nov. 23, 1999) entitled “Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes.”
Growth of nanowires having various aspect ratios, including nanowires with controlled diameters, is described in, e.g., Gudiksen et al (2000) “Diameter-selective synthesis of semiconductor nanowires” J. Am. Chem. Soc. 122, 8801-8802; Cui et al. (2001) “Diameter-controlled synthesis of single-crystal silicon nanowires” Appl. Phys. Lett. 78, 2214-2216; Gudiksen et al. (2001) “Synthetic control of the diameter and length of single crystal semiconductor nanowires” J. Phys. Chem. B 105, 4062-4064; Morales et al. (1998) “A laser ablation method for the synthesis of crystalline semiconductor nanowires” Science 279, 208-211; Duan et al. (2000) “General synthesis of compound semiconductor nanowires” Adv. Mater. 12, 298-302; Cui et al. (2000) “Doping and electrical transport in silicon nanowires” J. Phys. Chem. B 104, 5213-5216; Peng et al. (2000) “Shape control of CdSe nanocrystals” Nature 404, 59-61; Puntes et al. (2001) “Colloidal nanocrystal shape and size control: The case of cobalt” Science 291, 2115-2117; U.S. Pat. No. 6,306,736 to Alivisatos et al. (Oct. 23, 2001) entitled “Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process”; U.S. Pat. No. 6,225,198 to Alivisatos et al. (May 1, 2001) entitled “Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process”; U.S. Pat. No. 6,036,774 to Lieber et al. (Mar. 14, 2000) entitled “Method of producing metal oxide nanorods”; U.S. Pat. No. 5,897,945 to Lieber et al. (Apr. 27, 1999) entitled “Metal oxide nanorods”; U.S. Pat. No. 5,997,832 to Lieber et al. (Dec. 7, 1999) “Preparation of carbide nanorods”; Urbau et al. (2002) “Synthesis of single-crystalline perovskite nanowires composed of barium titanate and strontium titanate” J. Am. Chem. Soc., 124, 1186; and Yun et al. (2002) “Ferroelectric Properties of Individual Barium Titanate Nanowires Investigated by Scanned Probe Microscopy” Nanoletters 2, 447.
Growth of branched nanowires (e.g., nanotetrapods, tripods, bipods, and branched tetrapods) is described in, e.g., Jun et al. (2001) “Controlled synthesis of multi-armed CdS nanorod architectures using monosurfactant system” J. Am. Chem. Soc. 123, 5150-5151; and Manna et al. (2000) “Synthesis of Soluble and Processable Rod-, Arrow-, Teardrop-, and Tetrapod-Shaped CdSe Nanocrystals” J. Am. Chem. Soc. 122, 12700-12706.
Synthesis of nanoparticles is described in, e.g., U.S. Pat. No. 5,690,807 to Clark Jr. et al. (Nov. 25, 1997) entitled “Method for producing semiconductor particles”; U.S. Pat. No. 6,136,156 to El-Shall, et al. (Oct. 24, 2000) entitled “Nanoparticles of silicon oxide alloys”; U.S. Pat. No. 6,413,489 to Ying et al. (Jul. 2, 2002) entitled “Synthesis of nanometer-sized particles by reverse micelle mediated techniques”; and Liu et al. (2001) “Sol-Gel Synthesis of Free-Standing Ferroelectric Lead Zirconate Titanate Nanoparticles” J. Am. Chem. Soc. 123, 4344. Synthesis of nanoparticles is also described in the above citations for growth of nanocrystals, nanowires, and branched nanowires, where the resulting nanostructures have an aspect ratio less than about 1.5.
Synthesis of core-shell nanostructure heterostructures, namely nanocrystal and nanowire (e.g., nanorod) core-shell heterostructures, are described in, e.g., Peng et al. (1997) “Epitaxial growth of highly luminescent CdSe/CdS core/shell nanocrystals with photostability and electronic accessibility” J. Am. Chem. Soc. 119, 7019-7029; Dabbousi et al. (1997) “(CdSe)ZnS core-shell quantum dots: Synthesis and characterization of a size series of highly luminescent nanocrysallites” J. Phys. Chem. B 101, 9463-9475; Manna et al. (2002) “Epitaxial growth and photochemical annealing of graded CdS/ZnS shells on colloidal CdSe nanorods” J. Am. Chem. Soc. 124, 7136-7145; and Cao et al. (2000) “Growth and properties of semiconductor core/shell nanocrystals with InAs cores” J. Am. Chem. Soc. 122, 9692-9702. Similar approaches can be applied to growth of other core-shell nanostructures.
Growth of nanowire heterostructures in which the different materials are distributed at different locations along the long axis of the nanowire is described in, e.g., Gudiksen et al. (2002) “Growth of nanowire superlattice structures for nanoscale photonics and electronics” Nature 415, 617-620; Bjork et al. (2002) “One-dimensional steeplechase for electrons realized” Nano Letters 2, 86-90; Wu et al. (2002) “Block-by-block growth of single-crystalline Si/SiGe superlattice nanowires” Nano Letters 2, 83-86; and U.S. patent application 60/370,095 (Apr. 2, 2002) to Empedocles entitled “Nanowire heterostructures for encoding information.” Similar approaches can be applied to growth of other heterostructures.
Example Embodiments for Transferring NanowiresEmbodiments for applying nanostructures such as nanowires to surfaces are described in this section. In embodiments, one or more nanowires are provided proximate to an electrode pair on a transfer surface. The electrode pair is energized, whereby the nanowires become associated with the electrode pair. Subsequently, the nanowires are deposited from the electrode pairs to a destination surface.
The term “positioning” as used throughout refers to the alignment and association, as well as the deposition or coupling, of nanowires onto a surface, for example, an electrode pair. Positioning includes nanowires that are both aligned and non-aligned. The term “aligned” nanowires as used throughout refers to nanowires that are substantially parallel or oriented in the same or substantially same direction of one another (i.e. the nanowires are aligned in the same direction, or within about 45° of one another). The nanowires of the present invention are aligned such that they are all substantially parallel to one another and substantially perpendicular to each electrode of an electrode pair (e.g., aligned parallel to an axis through both electrodes) (though in additional embodiments, they can be aligned parallel to an electrode). Positioning of nanowires onto an electrode pair includes positioning the nanowires such that the nanowires span the electrode pair. In embodiments in which the nanowires are longer than the distance separating two electrodes of an electrode pair, the nanowires may extend beyond the electrodes.
Methods for providing nanowires for use in the methods and systems of the present invention are well known in the art. In an embodiment, the nanowires are provided in a suspension, which is a plurality of nanowires suspended in a liquid. In an embodiment, the liquid is an aqueous media, such as water or a solution of water, ions (including salts), and other components, for example surfactants. Additional examples of liquids suitable for preparing nanowire suspensions include, but are not limited, organic solvents, inorganic solvents, alcohols (e.g., isopropyl alcohol) (IPA), etc.
As used herein the phrase “proximate to an electrode pair” as it relates to providing the nanowires means that the nanowires are provided or positioned such that they can be acted upon by an electric field generated at the electrode pair. This is a distance from the electrode pair such that they can be associated with the electrodes. In example embodiments, the nanowires are provided such that they are at distance of less than about 10 mm from the electrode pairs. For example, the nanowires may be provided such that they are less than about 100 μm, less than about 50 μm, or less than about 1 μm from the electrode pair.
In embodiments, the present invention provides a system or apparatus for nanostructure alignment and deposition. For example,
Flowchart 300 begins with step 302. In step 302, at least one nanostructure is provided proximate to an electrode pair. For example, as shown in
In step 304, an electric field is generated by electrodes of the electrode pair to associate one or more nanostructures with the electrodes. For instance, an electrical potential may be coupled to electrode pair 208 to generate the electric field. The electric field generated by electrode pair 208 may be used to associate nanostructure(s) 204 with electrode pair 208 that are proximately located to electrode pair 208. As shown in
In step 306, the electrode pair is aligned with a region of the destination surface. For example, as shown in
In step 308, the one or more nanostructures are deposited from the electrode pair to the region. Nanostructure(s) 204 may be deposited on destination surface 210 in a variety of ways. Various example embodiments for depositing nanostructures on a surface are described in detail below.
In step 310, the electrode pair is removed from alignment with the region of the surface. For example, as shown in
Detailed example embodiments for nanostructure transfer system 200 and for performing flowchart 300 are described as follows. The embodiments are described below with respect to nanowires. These embodiments are provided for illustrative purposes, and are not intended to be limiting. It will be understood by persons skilled in the relevant art(s) that these embodiments may be used to transfer other types of nanostructures than just nanowires. Furthermore, these various embodiments may be adapted and/or combined in a variety of ways, as would be known to persons skilled in the relevant art(s) from the teachings herein.
Nanowires may be provided proximate to first and second electrodes 704 and 706 in a variety of ways according to step 302 of flowchart 300. For example,
Note that although electrode pair 208 is shown in
Nanowires 806 may be any suitable nanowire type described herein or otherwise known. For example, nanowires 806 may have a semiconductor core and one or more shell layers disposed about the core (i.e., the shell layers surround the core) (such as shown in
In an embodiment, container 802 receives a flow of solution 804 containing nanowires 806. For instance,
As shown in
Thus, in the embodiments described above, one or more nanowires 806 are provided by providing a suspension of nanowires (e.g., a nanowire “ink”) to electrode pair 208. As represented in
In an embodiment, container 802 can be stirred, vibrated, or otherwise moved to maintain a homogeneous suspension of nanowires 806. In another embodiment, where a stratified suspension of nanowires is desired, gravity, electric fields and/or an overflow by a nanowire-free solvent of similar or lower density can be used to create stratification. A stratified suspension of nanowires may be used in a variety of ways. For example, print head 702 may be positioned in a high nanowire-density region of the stratified suspension for deposition of nanowires, and subsequently positioned in a lower density, “clean solvent” region for removal of excess nanowires.
Additional methods for providing nanowires to an electrode pair are well known in the art, and include, but are not limited to, spray coaters, spray painting, meniscus coater, dip-coater, bar-coater, gravure coater, Meyer rod, doctor blade, extrusion, micro-gravure, web coaters, doctor blade coaters, in-line or ink jet printers.
As described above, a variety of configurations for electrode pair 208 may be used in embodiments. For example, electrode pair 208 may be fixed position electrodes. In another embodiment, electrode pair 208 may be configured to enable compliance with a destination surface to which they may be applied. For instance,
First and second cantilevers 1104 and 1106 are not substantially flexible in the plane of transfer surface 1102, but are flexible in a direction normal to the plane of transfer surface 1102 (shown as a Z-axis in
Cantilevers 1104 and 1106 may be any type and configuration of cantilever. In an embodiment, cantilevers 1104 and 1106 are micro-electromechanical system (MEMS) cantilevers.
According to step 304 of flowchart 300 (
Energizing electrode pair 208 to generate electric field 1402 can be performed during part or all of a nanowire alignment and deposition process. For example, electrode pair 208 may remain energized during step 306 of flowchart 300 (alignment of print head) and during a portion or all of step 308 of flowchart 300 (deposition of nanowires). In an example embodiment, electric field 1402 is generated by coupling (e.g., using wires or other connection) first electrode 704 to a positive electrode terminal of voltage source 1302, and coupling second electrode 706 to a negative electrode terminal of voltage source 1302. When an electric current is switched on and supplied by electrical signal 1304, the negative and positive terminals transfer charge to electrodes 704 and 706 positioned on transfer surface 206, thereby generating electric field 1402 between electrodes 704 and 706 of electrode pair 208. In embodiments, electric field 1402 can be constant electric field, a pulsed electric field such as a pulsed AC electric field, or other electric field type.
The energizing of electrode pair 208 to create electric field 1402 can also be caused by supplying an electromagnetic wave to electrode pair 208. As is well known in the art, waveguides of various dimensions and configurations (e.g., cylindrical, rectangular) can be used to direct and supply an electromagnetic wave (see e.g., Guru, B. S. et al., “Electromagnetic Field Theory Fundamentals,” Chapter 10, PWS Publishing Company, Boston, Mass. (1998)). Operation frequencies of waveguides for use in the practice of the present invention are readily determined by those of skill in the art, and may be in the range of about 100 MHz to 10 GHz, about 1 GHz-5 GHz, about 2-3 GHz, about 2.5 GHz, or about 2.45 GHz, for example.
As is further described below, as nanowires 806 encounter an AC electric field 1402 generated between electrodes 704 and 706, a field gradient results. A net dipole moment is produced in proximate nanowires 806 (e.g., nanowire 806a in
In embodiments, first and second electrodes 704 and 706 are separated by a distance that is less than, equal to, or greater than a long axis length of nanowires 806. Nanowires 806 of any length can be aligned and positioned using the methods of the present invention. In an embodiment, the distance between electrodes of an electrode pair is such that the nanowires extend just beyond the first edge of the electrode. In an embodiment, nanowires 806 extend just beyond a first edge and into a middle of each electrode, with tens of nanometers to several microns overlapping the electrode material at the end of a nanowire 806. Nanowires 806 that are shorter than the distance between electrodes 704 and 706 may be able to couple to only one electrode in a pair (if they couple at all), and thus may be removed during subsequent removing phases if desired. Similarly, nanowires 806 that are substantially longer than the distance between electrodes 704 and 706 hang over one or more of electrodes 704 and 706, and may be removed during subsequent removing phases (larger exposed surface area). Thus, this embodiment additionally provides a way to preferentially select nanowires 806 of a particular length from a suspension of a range of nanowire sizes, and align and deposit them onto an electrode pair 208. Embodiments may also associate and couple nanowires 806 that are “straight” rather than bent or crooked. Hence, such embodiments provide an added benefit of depositing preferably straight nanowires 806, rather than less preferred bent or crooked nanowires 806.
In addition to aligning the nanowires parallel to an AC electric field, the field gradient exerts a dielectrophoretic force on proximate nanowires 806, attracting them toward electrode pair 208.
Furthermore, in an embodiment, charge values of nanowires 806 and transfer surface 206 affect association or pinning of nanowires to electrode pair 208. For example,
In the associated, or pinned state, the nanowires are aligned parallel to the electric field, but are sufficiently mobile along the electrode edges (i.e. in a plane just above the surface of the electrodes). For example,
In the associated or pinned state, nanowires 1702 are free to rearrange, migrate and/or align along the length of the electrodes 704 and 706. Nanowires 1702 that are already substantially aligned with electric field 1402 will tend to migrate along electrode pair 208 until contacting, and/or being repelled by, a nearest neighbor nanowire. Nanowires 1702 that are not substantially aligned will tend to migrate such that they become aligned as they contact, and/or are repelled by, nearest neighbor nanowires and, an equilibrium between the various forces acting on nanowires 1702 is reached. The lateral mobility (i.e., along electrode pairs 208, perpendicular to a direction of electric field 1402) of nanowires 1702 allows them to accommodate a chronological sequence of alignment and association events without giving rise to nanowire clumping. That is, as nanowires are continuously supplied to electrode pair 208 (i.e., from a suspension) additional nanowires are able to associate with the electrodes, as the nanowires that are previously associated are freely mobile such that they move out of the way to accommodate additional nanowires.
For further example description regarding the association of nanowires with electrode pairs, various nanowire densities, alternating current frequencies, modulating of the electric field, “locking” nanowires to an electrode pair, etc., refer to co-pending U.S. Appl. No. 60/857,765, filed Nov. 9, 2006, titled “Methods for Nanowire Alignment and Deposition,” which is incorporated by reference herein in its entirety.
Following the associating of nanowires 1702 with electrodes 704 and 706, uncoupled nanowires can then be removed from electrode pair 208 so as to substantially eliminate nanowires that are not fully aligned, not fully coupled, overlapped, crossing, or otherwise not ideally coupled to electrode pair 208. Nanowires that are to be removed following the coupling phase are described herein as “uncoupled nanowires.” Any suitable method for removing uncoupled nanowires can be used. For example, the uncoupled nanowires can be removed using tweezers (e.g., optical tweezers, see, e.g., U.S. Pat. Nos. 6,941,033, 6,897,950 and 6,846,084, the disclosures of each of which are incorporated herein by reference in their entireties) or similar instrument, or by shaking or physically dislodging the uncoupled nanowires. Suitably, uncoupled nanowires are removed by flushing away the nanowires. As used herein, the term “flushing away” includes processes where a fluid (either gaseous or liquid phase) is flowed over or around the nanowires so as to remove them from the electrode pairs. Nanowires that are crossed can be uncrossed using a suitably modulated electric field, and a third electrode can be used to remove “uncoupled nanowires,” such as dielectrophoretically or electroosmotically. Uncoupled nanowires can also be removed inertially, and by other techniques.
According to step 306 of flowchart 300 (
Substrate 212 may be any type of structure suitable for placement of nanostructures. For example, substrate 212 may be formed of a variety of materials, including a semiconductor material (e.g., silicon, GaAs, etc.), a polymer (e.g., a plastic material), glass, a ceramic material, a composite material, a printed circuit board (PCB), etc.
Note that
Note that in an embodiment, as shown in
In
Note that in an embodiment where a print head is aligned with a destination surface in solution, the solution between the print head and destination surface will be displaced during alignment. If the solution is displaced laterally, this may cause problems with displacing associated nanowires, with increasing an area of the print head, and/or further problems.
According to step 308 of flowchart 300 (
For example,
For example,
Furthermore, as shown in
As shown in
The transfer of nanowires 1702 from transfer surface 206 onto destination surface 210 is achieved by first “weakly” pinning nanowires 1702 on transfer surface 206 at low electric fields and low frequencies, “strongly” pinning nanowires 1702 on transfer surface 206 using low electric fields and high frequencies, moving transfer surface 206 to close proximity with destination surface 210, and finally releasing nanowires 1702 from potential minimum 3006 of transfer surface 206 by reducing the AC field on electrodes 704 and 706 of transfer surface 206. Due to the electrostatic repulsion represented by a potential maximum 3010 between nanowires 1702 and transfer surface 206 (e.g. layer 2902 on transfer surface 206) nanowires 1702 move away from transfer surface 206 after reduction of the AC attractive field. Within the rotational diffusion time (i.e. time required for nanowires to be rotated by an angle θ from a pre-aligned direction while subjected to gravity and Brownian motion) nanowires 1702 maintain the desired alignment determined by the AC field across electrodes 704 and 706 on transfer surface 206. The close proximity (e.g., ˜1 μm) of the pre-aligned nanowires 1702 in solution to destination surface 210 enables a transfer onto destination surface 210 due to the electrostatic attraction represented by potential minimum 3008 (e.g. layer 2904 on destination surface 210). An efficient transfer of nanowires 1702 is enabled when the rotational diffusion time is large compared to the translational diffusion time for motion of nanowires from potential minimum 3006 to potential minimum 3008. Functional layers on nanowires 1702 and on destination surface 210 can be used to minimize the translational diffusion time without affecting the rotational diffusion time.
Note that in an embodiment, ultrasonic excitation/vibration can be used to enhance the process just described. For example,
Ultrasonic vibration source 3152 includes a piezoelectric transducer or other ultrasonic vibration source to ultrasonically vibrate substrate 212, and thus to ultrasonically vibrate destination surface 210. Furthermore, when transfer surface 206 and destination surface 210 are brought near each other, spacers 2302 (on print head 702 and/or substrate 212) contact print head 702 and destination surface 210 together. Thus, ultrasonic vibration source 3152 also vibrates print head 702 and transfer surface 206. Because ultrasonic vibration source 3152 vibrates both transfer surface 206 and destination surface 210, they vibrate synchronously, such that they both vibrate in the same direction simultaneously. This causes less turbulence than when only one of transfer surface 206 and destination surface 210 vibrate, and thus nanowires 1702 are better able to retain their alignment while being transferred (e.g., by gravity, electrostatic attraction, etc.) from transfer surface 206 to destination surface 210.
In an example embodiment, transfer surface 206 and/or destination surface 210 may be ultrasonically vibrated at relatively high frequency, such as 10 KHz, with a low amplitude, such as 50-100 microns, to effectively transfer nanowires 1702 from transfer surface 206 to destination surface 210. A variety of other combinations of displacement amplitude (X-axis 3172) and displacement frequency (Y-axis 3174) combinations are apparent from plot 3170, and may be used to cause wire displacement (Z-axis 3176) to transfer nanowires, as desired for a particular application.
It is noted that the above described embodiments for depositing nanowires on a destination surface according to step 308 of flowchart 300 (
According to step 310 of flowchart 300 (
Furthermore, flowchart 300 is adaptable to using multiple electrode pairs on a single transfer surface to deposit groups of nanowires on substrates in parallel. For example,
Thus, in an embodiment, each step of flowchart 300 shown in
In step 306, in parallel with aligning first electrode pair 208a with first region 1904a, second electrode pair 208b can be aligned with second region 1904b. In step 308, in parallel with depositing nanowires 1702a from first electrode pair 208a to first region 1904a, nanowires 1702b can be deposited from second electrode pair 208b to second region 1904b. In step 310, first and second electrode pairs 208a and 208b can be removed from alignment with their respective regions in parallel, by withdrawing print head 3402 from destination surface 210.
Note that any number of electrode pairs may be formed on a transfer surface to be used to transfer any number of corresponding sets of nanowires in parallel, in a similar fashion to the configuration of
Embodiments are described in this section for applying electrical devices, such as integrated circuits, electrical components, semiconductor die, optical devices, etc., to surfaces in a similar manner as described above for nanowires. In embodiments, one or more electrical devices are provided proximate to an electrode pair on a transfer surface. The electrode pair is energized such that an electrical device becomes associated with the electrode pair. Subsequently, the electrical device is deposited from the electrode pair to a destination surface.
Flowchart 3500 begins with step 3502. In step 3502, at least one electrical device is provided proximate to an electrode pair. For example, as shown in
In step 3504, an electric field is generated by electrodes of the electrode pair to associate an electrical device with the electrodes. For instance, an electrical potential may be coupled to electrode pair 208 to generate the electric field. The electric field generated by electrode pair 208 may be used to associate one of electrical devices 3602 with electrode pair 208 that is proximately located to electrode pair 208. As shown in
The example embodiments described above for generating an electric field by an electrode pair to associate nanostructures are adaptable to associating electrical devices. For example, as described with respect to
Furthermore, in an embodiment, the field gradient exerts a dielectrophoretic force on proximate electrical device 3602a, attracting it toward electrode pair 208, as described above for nanowires with respect to
As mentioned above, electrical devices 3602 in
In step 3506, the electrode pair is aligned with a region of the destination surface. For example, as shown in
In step 3508, the electrical device is deposited from the electrode pair to the region. Electrical device 3602a may be deposited on destination surface 210 in a variety of ways. Various example embodiments for depositing nanostructures on a surface are described in detail above. For example, the embodiments described above with respect to
In step 3510, the electrode pair is removed from alignment with the region of the surface. For example, as shown in
Using the techniques described herein, complex electrical circuits can be formed, by using print heads to transfer nanostructures and electrical devices to substrates.
Further Print Head EmbodimentsFurther embodiments are described in this section for applying nanostructures to surfaces using print heads. Print heads used to “print” nanowires onto a substrate in the presence of a fluid, as described above, may cause a shear force that is orthogonal to the motion of the print head as the print head approaches the substrate. As a result, the fluid is forced out of the region between the print head and the substrate due. This fluid shear can displace the nanowires laterally, causing the nanowires to be misplaced in the printing process.
For example,
During the transfer process, print head 702 is moved towards substrate 212 in the direction of arrow 4002, reducing a distance between transfer surface 206 and destination surface 210. Arrows 4006 indicate directions of flow of solution 4004 as print head 4002 is moved towards substrate 212, as solution 4004 is forced out of the region between transfer surface 206 and destination surface 210. Referring to
As indicted in
In embodiments, drain holes are formed in a print head to remove fluid from the region between the print head and the destination surface as the print head approaches the destination surface. The drain holes reduce a shear force on the nanowires, to enable the nanowires to be more reliably transferred from the print head to the destination surface. For example
In step 4402, a transfer surface of a print head is positioned adjacent to a destination surface. For instance, as shown in
In step 4404, a distance between the transfer surface and the destination surface is reduced. Referring to
In step 4406, a fluid is received through at least one opening in the transfer surface from between the transfer surface and the destination surface during step 4404. As indicated by arrows 4206 in
In step 4408, a nanowire associated with the transfer surface is deposited to the destination surface. For instance,
Although two openings 4204 (openings 4204a and 4204b) are shown in
Furthermore, openings 4204 may have any distribution/geometry relative to electrodes 704 and 706 to further reduce the shear force. For example, as shown in
Furthermore, as shown in
Although openings 4204 are shown in
In the example of
Nanostructures and/or contaminants may become attached to transfer surfaces of print heads, causing degradation in performance. In embodiments, the transfer surface of nanostructure print heads may be treated to prevent contaminants from sticking, and/to increase a durability of the transfer surface. Such embodiments may be particularly useful to extend a lifetime of a print head/transfer surface when print heads/transfer surfaces are expensive to replace. For example, a coating may be applied to the transfer surface, such as a coating of a non-stick material. In an embodiment, the coating may be removable. In this manner, the coating may be removed and reapplied as needed when a coating wears out, rather than having to dispose of the print head completely.
For instance,
Example advantages of non-stick material layer 4702 on transfer surface 206 include preventing nanowire adhesion and sticking, enabling the use of a higher nanowire capture voltage (e.g., during step 304 of flowchart 300 in
Non-stick material layer 4702 may be formed on transfer surface 206 in any manner, including by coating transfer surface 206 from a solution (i.e., spin coating or dip coating) or by a vapor phase deposition process. Non-stick material layer 4702 may be configured to have weak adhesion properties, such as adhesion properties characterized through van der Waals forces. Transfer surface 206 may be treated with adhesion promoters to prevent non-stick material layer 4702 from delaminating from transfer surface 206. Example materials for non-stick material layer 4702 include materials that have very low van der Waals force attraction with inorganic materials (contamination and nanowires), such as organic molecules or fluorinated organics (e.g., Teflon). A fluorinated organic material, such as Teflon, can have van der Waals forces 3 orders of magnitude lower than a typical oxide surface, thus making the strength of adhesion of contaminants to transfer surface 206 relatively weak. A thickness and/or chemistry of non-stick material layer 4702 may be selected as desired for the particular application.
In addition, as described above, non-stick material layer 4702 may be removable. For instance, if nanowires and/or other contamination does adhere to transfer surface 206 after one or more uses, non-stick material layer 4702 may be removed using solvents, plasma, thermal decomposition, or other removal material or technique. After removal of non-stick material layer 4702, a fresh replacement coating of non-stick material layer 4702 may be formed on transfer surface 206. This replacement process is simpler and less expensive than manufacturing a replacement print head 4700, which may be relatively expensive.
For instance, another type of non-stick material that may be applied to transfer surface 206, is a film of a material such as SiO2 or Si3N4. Such a film may be deposited on transfer surface 206 according to a plasma enhanced chemical vapor deposition (PECVD) process or other process. Such a film may prevent nanowires from sticking to transfer surface 206 by static charge. Furthermore, such a film may be removed after use, and reapplied to transfer surface 206, as needed, which may enable a lifespan of transfer surface 206 to be increased.
Example Nanostructure Printing Processes and SystemsExample embodiments are described in this section for nanostructure printing processes and systems. Embodiments are described for fabricating devices that incorporate nanostructures. These embodiments are provided for illustrative purposes, and are not intended to be limiting.
For example,
System 4800 is described with respect to flowcharts 4900 and 5000 shown in
Flowchart 4900 is first described. In step 4902 of flowchart 4900, nanostructures are associated with transfer surfaces of print heads. For example, as shown in
For example,
Although not shown in
During or after step 4902, print head 4810 of
Excess nanowires 5110, such as nanowire 5110c, which may be desired to be flushed from transfer surfaces 206, are nanowires that may be weakly associated with a transfer surface 206, that may have become entangled with other nanowires 5110 that are associated, and/or that may have become otherwise attached to (but not associated with) a surface of print head 4810. For example, nanowire 5110c is shown in
Referring back to flowchart 4900, in step 4904, an inspection of the print heads is performed. For example, as shown in
For instance,
For example, in
In step 4906, one or more print heads are selected based on the inspection. One or more print heads that passed inspection in step 4904 may be selected. In the current example, because inspection device 5302 determined that print heads 4810b and 4810c passed inspection, while print head 4810a failed inspection, print heads 4810b and 4810c may be selected for further processing in system 4800. Note that in an embodiment, an arrangement of nanowires 5110 at a print head 4810 that failed inspection may be repaired. For example, in the current example, after transfer surface 206c was determined (in step 4904) to be lacking a sufficient number of nanowires, one or more additional nanowires 5110 may be associated with transfer surface 206c. Subsequently, print head 4810a may be re-inspected (repeat step 4904). If print head 4810a passes the re-inspection, print head 4810a may be selected in step 4906. Example embodiments for repairing arrangements of nanostructures on surfaces (e.g., transfer surfaces, destination surfaces) are described in detail further below.
In step 4908, the nanostructures are transferred from the selected print head(s) to a destination surface. For example, as shown in
In embodiments, printing station 4806 may be configured to transfer nanostructures from print heads 4810 to panel 4816 in any manner described elsewhere herein, such as described above with respect to flowchart 300 in
In step 4910, the print heads are cleaned. For example, as shown in
For instance,
As shown in
Flowchart 5000, which relates to a pipeline of destination panels, is now described. In step 5002 of flowchart 5000, the nanostructures are received on the destination surface. For example, as shown in
In step 5004, the placement of received nanostructures on the destination surface is repaired. Step 5004 is optional. For example, as shown in
For example, in
As shown in
In step 5006, the destination surface is dried. For example, as shown in
As shown in
Nanostructure printing system 4800 includes printing station 4806, which in the example of
System 6100 is described with respect to flowcharts 6200 and 6300 shown in
Flowchart 6200 is first described. In step 6202 of flowchart 6200, nanostructures are associated with transfer surfaces of print heads. For example, as shown in
In step 6204, the print heads are dried. For example, as shown in
In step 6206, placement of nanostructures on one or more print heads is repaired. Step 6206 is optional. For example, as shown in
In step 6208, the nanostructures are transferred from one or more of the print heads to a destination surface. For example, as shown in
In an embodiment, printing station 6108 may be configured similarly to printing station 4806 shown in
In step 6210, the print heads are cleaned. For example, as shown in
Flowchart 6300, which relates to a pipeline of destination panels for system 6100, is now described. In step 6302 of flowchart 6300, the nanostructures are received on the destination surface. For example, as described above (with respect to step 6208 of flowchart 6200), nanostructures are transferred to panel 6116 by printing station 6108.
In step 6302, placement of the received nanostructures is repaired on destination surface. Step 6302 is optional. For example, as shown in
As shown in
This section describes images captured during a nanostructure transfer process performed according to an embodiment of the present invention.
Example electronic devices and systems that can be formed according to embodiments of the present invention are described below.
Use of Nanowires and Electrical Devices Deposited According to the Present Invention in Exemplary Devices and ApplicationsNumerous electronic devices and systems can incorporate semiconductor or other type devices with thin films of nanowires and/or electrical devices deposited according the methods of the present invention. Some example applications for the present invention are described below or elsewhere herein for illustrative purposes, and are not limiting. The applications described herein can include aligned or non-aligned thin films of nanowires, and can include composite or non-composite thin films of nanowires.
Semiconductor devices (or other type devices) can be coupled to signals of other electronic circuits, and/or can be integrated with other electronic circuits. Semiconductor devices can be formed on large substrates, which can be subsequently separated or diced into smaller substrates. Furthermore, on large substrates (i.e., substrates substantially larger than conventional semiconductor wafers), semiconductor devices formed thereon can be interconnected.
The nanowires deposited by the processes and methods of the present invention can also be incorporated in applications requiring a single semiconductor device, and in multiple semiconductor devices. For example, the nanowires deposited by the processes and methods of the present invention are particularly applicable to large area, macro electronic substrates on which a plurality of semiconductor devices are formed. Such electronic devices can include display driving circuits for active matrix liquid crystal displays (LCDs), organic LED displays, field emission displays. Other active displays can be formed from a nanowire-polymer, quantum dots-polymer composite (the composite can function both as the emitter and active driving matrix). The nanowires deposited by the processes and methods of the present invention are also applicable to smart libraries, credit cards, large area array sensors, and radio-frequency identification (RFID) tags, including smart cards, smart inventory tags, and the like.
The nanowires deposited by the processes and methods of the present invention are also applicable to digital and analog circuit applications. In particular, the nanowires deposited by the processes and methods of the present invention are useful in applications that require ultra large-scale integration on a large area substrate. For example, a thin film of nanowires deposited by the processes and methods of the present invention can be implemented in logic circuits, memory circuits, processors, amplifiers, and other digital and analog circuits.
The nanowires deposited by the processes and methods of the present invention can be applied to photovoltaic applications. In such applications, a clear conducting substrate is used to enhance the photovoltaic properties of the particular photovoltaic device. For example, such a clear conducting substrate can be used as a flexible, large-area replacement for indium tin oxide (ITO) or the like. A substrate can be coated with a thin film of nanowires that is formed to have a large bandgap, i.e., greater than visible light so that it would be non-absorbing, but would be formed to have either the HOMO or LUMO bands aligned with the active material of a photovoltaic device that would be formed on top of it. Clear conductors can be located on two sides of the absorbing photovoltaic material to carry away current from the photovoltaic device. Two different nanowire materials can be chosen, one having the HOMO aligned with that of the photovoltaic material HOMO band, and the other having the LUMO aligned with the LUMO band of the photovoltaic material. The bandgaps of the two nanowires materials can be chosen to be much larger than that of the photovoltaic material. The nanowires, according to this embodiment, can be lightly doped to decrease the resistance of the thin films of nanowires, while permitting the substrate to remain mostly non-absorbing.
Hence, a wide range of military and consumer goods can incorporate the nanowires and electrical devices deposited by the processes and methods of the present invention. For example, such goods can include personal computers, workstations, servers, networking devices, handheld electronic devices such as PDAs and palm pilots, telephones (e.g., cellular and standard), radios, televisions, electronic games and game systems, home security systems, automobiles, aircraft, boats, other household and commercial appliances, and the like.
Exemplary embodiments of the present invention have been presented. The invention is not limited to these examples. These examples are presented herein for purposes of illustration, and not limitation. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the invention.
All publications, patents and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference.
Example EmbodimentsIn an embodiment, a method for transferring nanowires to a destination surface includes providing at least one nanowire proximate to an electrode pair, generating an electric field with electrodes of the electrode pair to associate the at least one nanowire with the electrodes, aligning the electrode pair with a region of the destination surface, and depositing the at least one nanowire from the electrode pair to the region.
The transfer surface may be configured to have a first electric charge.
The first electric charge may apply a repulsive electrostatic force to the at least one nanowire, and the electric field may be configured to attract the at least one nanowire to the transfer surface against the repulsive electrostatic force.
The electric field may be biased with an alternating current (AC) field to attract the at least one nanowire to the transfer surface.
The electric field may be biased with a second AC field to enable the at least one nanowire to move toward the destination surface.
The destination surface may be configured to have a second electric charge that is opposite the first electric charge.
The at least one nanowire may be enabled to be attracted to the destination surface by an attractive electrostatic force of the second electric charge by reducing a distance between the at least one nanowire and the destination surface.
The at least one nanowire may be attracted toward the destination surface with the second electric charge.
The transfer surface may be ultrasonically vibrated to enable an attractive electrostatic force of the second electric charge to attract the at least one nanowire toward the destination surface.
Both the transfer surface and destination surface may be ultrasonically vibrated.
The transfer surface and destination surface may be ultrasonically vibrated synchronously.
A vacuum may be applied from the destination surface to the transfer surface to move the at least one nanowire toward the destination surface.
A second electric field associated with the destination surface may be generated to attract the at least one nanowire toward the destination surface.
Generation of the electric field may be ceased.
The destination surface may be configured to have a hydrophilic property to attract a solution containing the at least one nanowire toward the destination surface.
The transfer surface may be configured to have a hydrophobic property to repel a solution containing the at least one nanowire.
A solution containing the at least one nanowire may be flowed on the electrode pair.
A rate of flow of the solution on the electrode pair may be varied.
The electrode pair may include a first electrode and a second electrode, and the at least one nanowire may include a first nanowire. A first end of the first nanowire may be caused to be positioned adjacent to a surface of the first electrode, and a second end of the first nanowire may be caused to be positioned adjacent to a surface of the second electrode.
The at least one nanowire may be caused to align substantially in parallel with an axis through the first and second electrodes.
The at least one nanowire may be positioned such that the first and second ends are not in contact with the first and second electrodes.
The region may include an electrical contact pair. The electrode pair may be contacted with the electrical contact pair.
The electrode pair may be contacted with the destination surface.
A cantilever that mounts a first electrode of the electrode pair may be caused to flex due to the contacting.
A pair of cantilevers that mount the electrode pair may be caused to flex due to the contacting.
The electrode pair may be positioned adjacent to the surface.
The electrode pair may be removed from alignment with the region of the destination surface.
A second at least one nanowire may be provided proximate to the electrode pair.
A second electric field may be generated with the electrodes of the electrode pair to associate the second at least one nanowire with the electrodes. The electrode pair may be aligned with a second region of the surface. The at least one nanowire may be deposited from the electrode pair to the second region.
The first electrode pair and a second electrode pair may be on a common transfer surface. In parallel with the providing the first at least one nanowire proximate to the first electrode pair, a second at least one nanowire proximate may be provided to the second electrode pair. In parallel with the generating the first electric field, a second electric field may be generated with second electrodes of the second electrode pair to associate the second at least one nanowire with the second electrodes. In parallel with the aligning the first electrode pair with the first region of the surface, the second electrode pair may be aligned with a second region of the surface. In parallel with the depositing the first at least one nanowire from the first electrode pair to the first region, the second at least one nanowire may be deposited from the second electrode pair to the second region.
Uncoupled nanowires may be removed from the electrode pair.
In another embodiment, a system for transferring nanowires to a destination may include a body having a transfer surface, an electrode pair on the transfer surface, a suspension that includes a plurality of nanowires provided proximate to the electrode pair, a signal generator coupled to the electrode pair, wherein the signal generator is configured to enable electrodes of the electrode pair to generate an electric field to associate at least one nanowire of the plurality of nanowires with the electrodes, and an alignment mechanism configured to align the electrode pair with a region of the destination surface to enable the associated at least one nanowire to be deposited from the electrode pair to the region.
The transfer surface may have a first electric charge.
The first electric charge may apply a repulsive electrostatic force to the at least one nanowire, and the electric field may attract the at least one nanowire to the transfer surface against the repulsive electrostatic force.
The signal generator may bias the electric field with an alternating current (AC) field to attract the at least one nanowire to the transfer surface.
The signal generator may bias the electric field with a second AC field to enable the associated at least one nanowire to move toward the destination surface.
The destination surface may have a second electric charge that is opposite the first electric charge.
The alignment mechanism may be configured to reduce a distance between the at least one nanowire and the destination surface to enable the associated at least one nanowire to be attracted to the destination surface by an attractive electrostatic force of the second electric charge.
The associated at least one nanowire may be attracted toward the destination surface by the second electric charge.
The system may further include an ultrasonic vibration source configured to vibrate the transfer surface to enable an attractive electrostatic force of the second electric charge to attract the associated at least one nanowire toward the destination surface.
The ultrasonic vibration source may be configured to vibrate both the transfer surface and destination surface.
The ultrasonic vibration source may be configured to vibrate the transfer surface and destination surface synchronously.
The system may further include a vacuum source configured to apply a vacuum from the destination surface to the transfer surface to move the associated at least one nanowire toward the destination surface.
The system may further include an electric field source configured to generate a second electric field associated with the destination surface to attract the associated at least one nanowire toward the destination surface.
The signal generator may be configured to reduce an intensity of the electric field to enable the associated at least one nanowire to be attracted toward the destination surface.
The destination surface may be configured to have a hydrophilic property to attract a fluid containing the associated at least one nanowire toward the destination surface.
The transfer surface may be configured to have a hydrophobic property to repel the fluid containing the associated at least one nanowire.
The system may further include a container that contains the suspension and the electrode pair.
The suspension may be flowed over the electrode pair.
The electrode pair may include a first electrode and a second electrode, and the at least one nanowire may include a first nanowire. The electric field may cause a first end of the first nanowire to be positioned adjacent to a surface of the first electrode, and a second end of the first nanowire to be positioned adjacent to a surface of the second electrode.
The electric field may align the at least one nanowire substantially in parallel with an axis through the first and second electrodes.
The electric field may position the at least one nanowire such that the first and second ends are not in contact with the first and second electrodes.
The region may include an electrical contact pair. The alignment mechanism may be configured to contact the electrode pair with the electrical contact pair.
The alignment mechanism may be configured contact the electrode pair with the destination surface.
The transfer surface may have a cantilever that mounts a first electrode of the electrode pair. The cantilever is configured to flex if the electrode pair contacts the destination surface.
The transfer surface may have a pair of cantilevers that mount first and second electrodes of the electrode pair. The pair of cantilevers is configured to flex if the electrode pair contacts the destination surface.
The alignment mechanism may be configured to position the electrode pair adjacent to the surface.
The system may further include a plurality of spacers on the transfer surface.
The alignment mechanism may be configured to remove the electrode pair from alignment with the region of the destination surface after the associated at least one nanowire is deposited.
A second electrode pair may be on the transfer surface.
In another embodiment, a method for applying nanowires to a destination surface may include aligning an electrode pair having an associated at least one nanowire with a region of the destination surface, and depositing the at least one nanowire from the electrode pair to the region.
In another embodiment, a system for transferring electrical devices to a destination surface may include a body having a transfer surface, an electrode pair on the transfer surface, a suspension that includes a plurality of electrical devices provided proximate to the electrode pair, a signal generator coupled to the electrode pair, wherein the signal generator is configured to enable electrodes of the electrode pair to generate an electric field to associate an electrical device of the plurality of electrical devices with the electrodes, and an alignment mechanism configured to align the electrode pair with a region of the destination surface to enable the associated electrical device to be deposited from the electrode pair to the region.
The system may further include an ultrasonic vibration source configured to vibrate the transfer surface to enable an attractive electrostatic force to attract the associated electrical device toward the destination surface.
The ultrasonic vibration source may be configured to vibrate both the transfer surface and destination surface.
The ultrasonic vibration source may be configured to vibrate the transfer surface and destination surface synchronously.
The system may further include an ultrasonic vibration source configured to vibrate the transfer surface to enable an attractive electrostatic force to attract the associated electrical device toward the destination surface.
The ultrasonic vibration source may be configured to vibrate both the transfer surface and destination surface.
The ultrasonic vibration source may be configured to vibrate the transfer surface and destination surface synchronously.
In another embodiment, a method for transferring nanowires to a destination surface may include positioning a transfer surface of a print head adjacent to a destination surface, wherein a nanowire is associated with the transfer surface, reducing a distance between the transfer surface and the destination surface, receiving a fluid in at least one opening in the transfer surface from between the transfer surface and the destination surface during the reducing, and depositing the nanowire from the transfer surface to the destination surface.
The fluid may be received in first and second openings in the transfer surface, the nanowire being associated with the transfer surface at a location substantially midway between the first and second openings.
The first and second openings may each have a length that is greater than a length of a long axis of the nanowire.
The lengths of the first and second openings may be positioned in the transfer surface in parallel with the long axis of the nanowire.
A piston may be moved within each of the first and second openings to draw the fluid from between the transfer surface and the destination surface into the first and second openings.
In another embodiment, a system for transferring nanowires to a destination surface may include a body having a transfer surface, at least one opening in the transfer surface, and an electrode pair formed on the transfer surface. The electrode pair may be configured to generate an electric field to associate a nanowire with the electrode pair. The at least one opening may be configured to receive a fluid from between the transfer surface and the destination surface.
The at least one opening may be configured to receive the fluid from between the transfer surface and the destination surface when the transfer surface is being moved toward the destination surface.
The at least one opening may include a first opening and a second opening. The electrode pair may be configured to associate the nanowire with the transfer surface at a location substantially midway between the first and second openings.
The first and second openings may each have a length that is greater than a length of a long axis of the nanowire.
The first and second openings may be positioned in the transfer surface such that the lengths of the first and second openings are configured to be parallel with the long axis of the nanowire.
The system may further include a first piston in the first opening and a second piston in the second opening. The first and second pistons may be configured to draw the fluid from between the transfer surface and the destination surface into the first and second openings.
In another embodiment, a method for transferring nanowires to a destination substrate may include associating nanostructures with transfer surfaces of a plurality of print heads, performing an inspection of the transfer surfaces of the plurality of print heads, selecting at least one print head of the plurality of print heads based on the inspection, and transferring the nanostructures from the selected at least one print head to a plurality of regions of a surface of a destination substrate.
Excess nanostructures may be flushed from the transfer surfaces of the plurality of print heads.
The selected at least one print head may be cleaned after the transferring.
An inspection may be performed of the nanostructures transferred to the plurality of regions of the surface of the destination substrate.
An arrangement of nanostructures transferred to a region of the surface of the destination substrate in need of repair may be determined, and the determined arrangement of nanostructures may be repaired.
The transfer surfaces may be positioned in a suspension containing a plurality of nanostructures, and an electric field may be generated with electrodes of an electrode pair of each transfer surface to associate nanostructures with the electrode pair of each transfer surface.
The associated nanostructures may be deposited from at least one electrode pair of the selected at least one print head to the surface of the destination substrate.
In another embodiment, a method for transferring nanowires to a destination substrate may include associating nanostructures with transfer surfaces of a plurality of print heads, drying the transfer surfaces having associated nanostructures, performing an inspection of the dried transfer surfaces having associated nanostructures, and transferring the nanostructures from the dried transfer surfaces to a plurality of regions of a surface of the destination substrate.
An arrangement of nanostructures associated with a transfer surface of a print head in need of repair may be determined, and the determined arrangement of nanostructures may be repaired.
Excess nanostructures may be flushed from the transfer surfaces of the plurality of print heads prior to the drying.
The plurality of print heads may be cleaned after the transferring.
An inspection of the nanostructures transferred to the plurality of regions of the surface of the destination substrate may be performed.
An arrangement of nanostructures transferred to a region of the surface of the destination substrate in need of repair may be determined, and the determined arrangement of nanostructures may be repaired.
The transfer surfaces may be positioned in a suspension containing a plurality of nanostructures, and an electric field may be generated with electrodes of an electrode pair of each transfer surface to associate nanostructures with the electrode pair of each transfer surface.
The associated nanostructures may be deposited from at least one electrode pair of the selected at least one print head to the surface of the destination substrate.
In another embodiment, a system for transferring nanowires to a destination substrate may include an association station configured to receive a plurality of print heads, and to associate nanostructures with a transfer surface of each of the received plurality of print heads, a printing station configured to receive a destination substrate and at least one of the plurality of print heads, and to transfer the nanostructures from the received at least one of the plurality of print heads to a plurality of regions of a surface of the destination substrate, and a cleaning station configured to receive the plurality of print heads from the printing station, and to clean the received plurality of print heads.
The association station may be configured to flush excess nanostructures from the transfer surfaces of the plurality of print heads.
The system may further include a repair station configured to receive the destination substrate, and to perform an inspection of the nanostructures transferred to the plurality of regions of the surface of the destination substrate.
The repair station may be configured to determine an arrangement of nanostructures transferred to a region of the surface of the destination substrate in need of repair based on the inspection, and to repair the determined arrangement of nano structures.
The printing station may be configured to perform a wet transfer of the nano structures.
The system may further include an inspection station configured to receive the plurality of print heads from the association station, to perform an inspection of the transfer surfaces of the plurality of print heads, and to select at least one print head of the plurality of print heads based on the inspection. The printing station may be configured to transfer the nanostructures from the selected at least one print head to the plurality of regions of the surface of the destination substrate.
The system may further include a panel drying station configured to receive the destination substrate, and to dry the nanostructures transferred to the plurality of regions of the surface of the destination substrate.
The printing station may be configured to perform a dry transfer of the nano structures.
The system may further include a print head drying station configured to receive the plurality of print heads, and to dry the transfer surfaces and the nanostructures associated with the transfer surfaces of the plurality of print heads.
The system may further include a repair station configured to perform an inspection of the dried transfer surfaces having associated nanostructures, to determine an arrangement of nanostructures associated with a transfer surface of a print head in need of repair based on the inspection, and to repair the determined arrangement of nano structures.
Claims
1. A system for transferring nanowires to a destination surface, comprising:
- a body having a transfer surface;
- an electrode pair on the transfer surface;
- a suspension that includes a plurality of nanowires provided proximate to the electrode pair;
- a signal generator coupled to the electrode pair, wherein the signal generator is configured to enable electrodes of the electrode pair to generate an electric field to associate at least one nanowire of the plurality of nanowires with the electrodes; and
- an alignment mechanism configured to align the electrode pair with a region of the destination surface to enable the associated at least one nanowire to be deposited from the electrode pair to the region.
2. A system for applying nanowires to a destination surface, comprising:
- a body having a transfer surface; and
- an electrode pair formed on the transfer surface;
- wherein the electrode pair is configured to generate an electric field to associate a proximate at least one nanowire with the electrode pair; and
- wherein the electrode pair is configured to be aligned with a region of the destination surface to enable the associated at least one nanowire to be deposited from the electrode pair to the region.
3. A method for transferring electrical devices to a destination surface, comprising:
- providing at least one electrical device proximate to an electrode pair;
- generating an electric field with electrodes of the electrode pair to associate an electrical device with the electrodes;
- aligning the electrode pair with a region of the destination surface; and
- depositing the electrical device from the electrode pair to the region.
4. The method of claim 3, wherein the electrical device is an integrated circuit die, wherein said depositing comprises:
- depositing the integrated circuit die from the electrode pair to the region.
5. The method of claim 3, wherein the electrical device is one of an integrated circuit, an electrical component, or an optical device, wherein said depositing comprises:
- depositing the one of the integrated circuit, the electrical component, or the optical device from the electrode pair to the region.
6. The method of claim 3, wherein said depositing comprises:
- ultrasonically vibrating the transfer surface to enable an attractive electrostatic force to attract the electrical device toward the destination surface.
7. The method of claim 6, wherein said ultrasonically vibrating the transfer surface comprises:
- ultrasonically vibrating both the transfer surface and destination surface.
8. The method of claim 7, wherein said ultrasonically vibrating the transfer surface further comprises:
- ultrasonically vibrating the transfer surface and destination surface synchronously.
9. A system for transferring electrical devices to a destination surface, comprising:
- a body having a transfer surface;
- an electrode pair on the transfer surface;
- a suspension that includes a plurality of electrical devices provided proximate to the electrode pair;
- a signal generator coupled to the electrode pair, wherein the signal generator is configured to enable electrodes of the electrode pair to generate an electric field to associate an electrical device of the plurality of electrical devices with the electrodes; and
- an alignment mechanism configured to align the electrode pair with a region of the destination surface to enable the associated electrical device to be deposited from the electrode pair to the region.
10. The system of claim 9, wherein the electrical device is an integrated circuit die.
11. The system of claim 9, wherein the electrical device is one of an integrated circuit, an electrical component, or an optical device.
12. A system for applying electrical devices to a destination surface, comprising:
- a body having a transfer surface; and
- an electrode pair formed on the transfer surface;
- wherein the electrode pair is configured to generate an electric field to associate a proximate electrical device with the electrode pair; and
- wherein the electrode pair is configured to be aligned with a region of the destination surface to enable the associated electrical device to be deposited from the electrode pair to the region.
13. The system of claim 12, wherein the electrical device is an integrated circuit die.
14. The system of claim 12, wherein the electrical device is one of an integrated circuit, an electrical component, or an optical device.
15. A method for transferring nanowires to a destination surface, comprising:
- positioning a transfer surface of a print head adjacent to a destination surface, wherein a nanowire is associated with the transfer surface;
- reducing a distance between the transfer surface and the destination surface;
- receiving a fluid in at least one opening in the transfer surface from between the transfer surface and the destination surface during said reducing; and
- depositing the nanowire from the transfer surface to the destination surface.
16. A system for transferring nanowires to a destination surface, comprising:
- a body having a transfer surface;
- at least one opening in the transfer surface; and
- an electrode pair formed on the transfer surface;
- wherein the electrode pair is configured to generate an electric field to associate a nanowire with the electrode pair; and
- wherein the at least one opening is configured to receive a fluid from between the transfer surface and the destination surface.
17. A method for transferring nanowires to a destination substrate, comprising:
- associating nanostructures with transfer surfaces of a plurality of print heads;
- performing an inspection of the transfer surfaces of the plurality of print heads;
- selecting at least one print head of the plurality of print heads based on the inspection; and
- transferring the nanostructures from the selected at least one print head to a plurality of regions of a surface of a destination substrate.
18. A method for transferring nanowires to a destination substrate, comprising:
- associating nanostructures with transfer surfaces of a plurality of print heads;
- drying the transfer surfaces having associated nanostructures;
- performing an inspection of the dried transfer surfaces having associated nanostructures; and
- transferring the nanostructures from the dried transfer surfaces to a plurality of regions of a surface of the destination substrate.
19. A system for transferring nanowires to a destination substrate, comprising:
- an association station configured to receive a plurality of print heads, and to associate nanostructures with a transfer surface of each of the received plurality of print heads;
- a printing station configured to receive a destination substrate and at least one of the plurality of print heads, and to transfer the nanostructures from the received at least one of the plurality of print heads to a plurality of regions of a surface of the destination substrate; and
- a cleaning station configured to receive the plurality of print heads from the printing station, and to clean the received plurality of print heads.
20. A system for applying nanowires to a destination surface, comprising:
- a body having a transfer surface;
- a non-stick coating formed on the transfer surface; and
- an electrode pair formed on the transfer surface;
- wherein the electrode pair is configured to generate an electric field to associate a proximate at least one nanowire with the electrode pair; and
- wherein the electrode pair is configured to be aligned with a region of the destination surface to enable the associated at least one nanowire to be deposited from the electrode pair to the region.
21. A method for transferring nanowires to a destination substrate, comprising:
- associating nanostructures with transfer surfaces of a plurality of print heads;
- performing an inspection of the transfer surfaces of the plurality of print heads;
- determining an arrangement of nanostructures associated with a transfer surface of a print head of the plurality of print heads in need of repair;
- repairing the determined arrangement of nanostructures; and
- transferring the repaired arrangement of nanostructures from the transfer surface of the print head to a destination substrate.
Type: Application
Filed: Jan 19, 2011
Publication Date: Jul 7, 2011
Applicant: NANOSYS, INC. (Palo Alto, CA)
Inventors: J. Wallace Parce (Palo Alto, CA), James M. Hamilton (Sunnyvale, CA), Samuel Martin (Cupertino, CA), Erik Freer (Campbell, CA)
Application Number: 13/009,675
International Classification: B05D 1/04 (20060101); B05B 5/025 (20060101);
