Abstract: Spin-polarized electrons can be efficiently extracted from an n-doped semiconductor layer (n-S) by forming a modified Schottky contact with a ferromagnetic material (FM) and a ?-doped layer at an interface under forward bias voltage conditions. Due to spin-selection property of the FM-S junction, spin-polarized carriers appear in the n-doped semiconductor layer near the FM-S interface. If a FM-n-n?-p heterostructure is formed, where the n? region is a narrower gap semiconductor, polarized electrons from the n-S region and holes from the p-S region can diffuse into the n?-S region under the influence of independent voltages applied between the FM and n? regions and the n? and p regions. The polarized electrons and holes recombine in the n?-S region and produce polarized light. The polarization can be controlled and modulated by controlling the applied voltages.

Abstract: A SERS-active structure is disclosed that includes a substrate and at least two nanowires disposed on the substrate. Each of the at least two nanowires has a first end and a second end, the first end being attached to the substrate and the second end having a SERS-active tip. A SERS system is also disclosed that includes a SERS-active structure. Also disclosed are methods for forming a SERS-active structure and methods for performing SERS with SERS-active structures.

Abstract: A patterned array of metallic nanostructures and fabrication thereof is described. A plurality of nanowires is grown on a substrate, the plurality of nanowires being laterally arranged on the substrate in a predetermined array pattern. The plurality of nanowires is coated with a metal to generate a plurality of metal-coated nanowires. Vacancies between the metal-coated nanowires are filled in with a sacrificial material for stabilization, and the metal-coated nanowires are planarized. The sacrificial material is removed, the patterned array of metallic nanostructures being formed by the plurality of planarized metal-coated nanowires.

Abstract: An apparatus for controlling propagation of incident electromagnetic radiation is described, comprising a composite material having electromagnetically reactive cells of small dimension relative to a wavelength of the incident electromagnetic radiation. Each electromagnetically reactive cell comprises a metallic element and a substrate. An electron population within the substrate near the metallic element of at least one of the electromagnetically reactive cells is temporally controllable to allow temporal control of an associated effective refractive index encountered by the incident electromagnetic radiation while propagating through said composite material.

Abstract: An apparatus for controlling propagation of incident electromagnetic radiation is described, comprising a composite material having electromagnetically reactive cells of small dimension relative to a wavelength of the incident electromagnetic radiation. At least one of a capacitive and inductive property of at least one of the electromagnetically reactive cells is temporally controllable to allow temporal control of an associated effective refractive index encountered by the incident electromagnetic radiation while propagating through the composite material.

Abstract: A near-field scanning optical probe comprises an optical fiber for conducting imaging light therethrough, the fiber having at least a portion doped with an optical gain medium and further having a tapered end portion with a frustoconical wall and an end surface for emitting the imaging light. In use, pumping light and optionally imaging light are coupled into the optical fiber such that the pumping light excites the optical gain medium to a higher energy state to emit photons at the approximate wavelength of the imaging light desired, to thereby produce and optionally amplify the imaging light emitted by the probe.

Abstract: A composition of matter is provided that results in a change of electrical properties through intra-molecular charge transfer or inter-molecular charge transfer or charge transfer between a molecule and an electrode, wherein the charge transfer is induced by an electric field.

Abstract: Ultrafast square-law detectors amplify electric currents and electromagnetic waves with frequencies on the order of 100 GHz or more. The detectors use injection of spin-polarized electrons from a magnetic film or region into another magnetic film or region through a thin semiconductor control region. A signal current flowing through a conductive nanowire induces a magnetic field causing precession of electron spin injected inside the semiconductor layer and thereby changing the conductivity of the detector. With the magnetizations of the magnetic regions being parallel or antiparallel to each other, the resulting spin injection current includes a term proportional to the square of the signal current so that the detector behaves as a square-law detector. Such square-law detectors are magnetic-semiconductor heterostructures and can operate as a frequency doubler for millimeter electromagnetic waves.

Abstract: Ultrafast solid state amplifiers of electrical current, including power amplification devices, use injection of spin-polarized electrons from a magnetic region into another magnetic region through a semiconductor control region and electron spin precession inside the control region induced by magnetic field resulting from a current flowing through a conductive nanowire. The amplifiers may include magnet-semiconductor-magnet heterostructures and are able to operate on electric currents and electromagnetic waves having frequencies up to 100 GHz or more.

Abstract: Devices such as transistors, amplifiers, frequency multipliers, and square-law detectors use injection of spin-polarized electrons from one magnetic region, into another through a control region and spin precession of injected electrons in a magnetic field induced by current in a nanowire. In one configuration, the nanowire is also one of the magnetic regions and the control region is a semiconductor region between the magnetic nanowire and the other magnetic region. Alternatively, the nanowire is insulated from the control region and the two separate magnetic regions. The relative magnetizations of the magnetic regions can be selected to achieve desired device properties. A first voltage applied between one magnetic region and the other magnetic nanowire or region causes injection of spin-polarized electrons through the control region, and a second voltage applied between the ends of the nanowire causes a current and a magnetic field that rotates electron spins to control device conductivity.

Abstract: An electric field activated molecular system, preferably bi-stable, configured within an electric field generated by a pair of electrodes is provided for use, e.g., as electronic ink or other visual displays. The molecular system has an electric field induced band gap change that occurs via a change (reversible or irreversible) of the extent of the electron conjugation via chemical bonding change to change the band gap, wherein in a first state, there is substantial conjugation throughout the molecular system, resulting in a relatively smaller band gap, and wherein in a second state, the substantial conjugation is destroyed, resulting in a relatively larger band gap. The changing of substantial conjugation may be accomplished in one of the following ways: (1) charge separation or recombination accompanied by increasing or decreasing electron localization in the molecule; or (2) change of substantial conjugation via charge separation or recombination and&pgr;-bond breaking or making.

Abstract: A gated nanoscale switch operates as a resonant tunneling device. A conductive channel is formed of a pair of conductive molecular wires and a conductive nanoparticle. Each molecular wire is bound, at one end, to the conductive nanoparticle and, at the opposed end, to one of a pair of electrodes. The structure is located upon a dielectric layer that overlies a conductive substrate. The device may be arranged to operate as a switch with the conductive substrate acting as a gate electrode. Alternatively, the device may be employed to measure the electrical (current versus voltage) characteristics of the molecular wires.

Abstract: A route to the fabrication of electronic devices is provided, in which the devices consist of two crossed wires sandwiching an electrically addressable molecular species. The approach is extremely simple and inexpensive to implement, and scales from wire dimensions of several micrometers down to nanometer-scale dimensions. The electronic devices can be used to produce crossbar switch arrays, logic devices, memory devices, and communication and signal routing devices. The construction of molecular electronic devices is achieved on a length scale than can range from micrometers to nanometers via a straightforward and inexpensive chemical assembly procedure. The molecular switchable devices in the cross-bar geometry are configurable while the conformational change is controlled by intramolecular forces that are stronger than hydrogen bonding.

Abstract: An electric field activated molecular system, preferably bi-stable, configured within an electric field generated by a pair of electrodes is provided for use, e.g., as electronic ink or other visual displays. The molecular system has an electric field induced band gap change that occurs via a change (reversible or irreversible) of the extent of the electron conjugation via chemical bonding change to change the band gap, wherein in a first state, there is substantial conjugation throughout the molecular system, resulting in a relatively smaller band gap, and wherein in a second state, the substantial conjugation is destroyed, resulting in a relatively larger band gap. The changing of substantial conjugation may be accomplished in one of the following ways: (1) charge separation or recombination accompanied by increasing or decreasing electron localization in the molecule; or (2) change of substantial conjugation via charge separation or recombination and &pgr;-bond breaking or making.