Abstract: The present invention provides a superconducting switch which has a substrate base and a control line patterned thereon. A buffer layer is deposited on top of these and then a superconducting material is deposited and then patterned wherein the superconducting material forms a strip having multiple intersections with the control line. At each intersection between the control line and the superconducting strip is formed a superconducting gate due to the double step edge junction. The control line underneath provides (1) a means for constructing step edge weak link junctions; (2) a means for heating the weak link junctions; and (3) generating an electromagnetic field near the weak link junctions. In combination, a very small magnetic field can be used to decrease the critical current to a very low level.

Abstract: A Josephson junction device comprises a single crystalline substrate including a principal surface, an oxide layer formed on the principal surface of the substrate having a step on its surface and an oxide superconductor thin film formed on the surface of the oxide layer. The oxide superconductor thin film includes a first and a second portions respectively positioned above and below the step of the oxide layer, which are constituted of single crystals of the oxide superconductor, and a step-edge junction made up of a grain boundary on the step of the oxide layer, which constitutes a weak link of the Josephson junction.

Abstract: The present invention discloses a double poly metal oxide.backslash.nitride.backslash.oxide semiconductor electrically erasable programmable read only memory (EEPROM) for use in semiconductor memories. The EEPROM structure includes a select gate, an oxide.backslash.nitride.backslash.oxide layer, and a control gate. The control gate is formed on the oxide.backslash.nitride.backslash.oxide layer. A lightly doped drain (LDD) structure is formed adjacent to the drain and underneath the control gate.

Abstract: The optical response of high-quality epitaxial copper-oxide perovskite films on substrates such as LaGaO.sub.3 and SrTiO.sub.3 exhibits a nonbolometric component to a photoresponse at certain temperatures below the onset of the superconducting transition and when carrying bias currents of a certain magnitude. A nonbolometric superconductive photoresponsive cell and method employ such films. The photoresponsive cell and method of the invention can be used to detect electromagnetic radiation incident on the film and to switch or modulate electrical signals passing through the film.

Abstract: A method of fabricating a superconducting quantum interference device (DC-SQUID) constructed from short weak links with untrafine wires. The method comprises the following steps: successive forming a niobium nitride film and a silicon nitride film on a substrate; oblique etching of the niobium nitride film and said silicon nitride film with respect to the substrate by a reactive ion etching process using a mixture of oxygen and CF.sub.4 gases to form an olique edge; and successive forming a barrier thin film and a counterelectrode of niobium on the said edge. The short weak links wire fabricated by field evaporation technique. The counterelectrode material were field-evaporated and formed the conductive paths in the pinholes in the insulating thin film.

Abstract: A superconducting oxide thin film device is composed of a LaAlO.sub.3 substrate and a YBCO thin film with a BaCeO.sub.3 buffer layer disposed between the two. The adhesion between the film and the substrate is increased by the presence of the buffer layer. The buffer layer also inhibits peeling of the film from the substrate and diffusion of Ba from the film into the substrate.

Abstract: A Josephson junction device includes a substrate, an oxide thin film formed on a portion of the principal surface of the substrate, which is constituted of a single crystal of which lattices shift at angle of 45.degree. to that of the principal surface of the substrate. One of the two portions of the oxide superconductor thin film is formed on the oxide thin film and the other portion of the superconductor thin film is formed on the principal surface of the substrate directly so that the lattices of the two portions of the oxide superconductor thin film are respectively linear up to those of the oxide thin film and the principal surface of the substrate and the grain boundary. The grain boundary which constitutes a weak link of the Josephson junction is formed just on the step portion formed of the oxide thin film.

Abstract: A Josephson junction device is disclosed that includes a single crystalline substrate having a NaCl type crystal structure. The device includes a principal surface having two horizontal planes and a slope inclined at an angle of 5.degree. to 30.degree. between the two horizontal planes. An oxide superconductor thin film is formed on the principal surface of the substrate, which includes first and a second superconducting portions of a first single crystalline oxide superconductor and a second single crystalline oxide superconductor respectively positioned on the two horizontal planes of the substrate. A junction portion of a single crystalline oxide superconductor has a different crystal orientation from the first and the second superconducting portions, and is positioned on the slope of the substrate. Two grain boundaries between each of the first and the second superconducting portions and the junction portion constitute one weak link of the Josephson junction.

Abstract: A SQUID includes a substrate and a superconducting current path of a patterned oxide superconductor material thin film formed on a surface of the substrate. A c-axis of an oxide crystal of the oxide superconductor material thin film is oriented in parallel to the surface of the substrate.

Abstract: A superconducting device low in power dissipation and high in operating speed is fabricated by use of a combination of a superconductor material and a semiconductor material. The superconducting device having a low power dissipation and high operating speed characteristic according to the present invention is suitable for configuring a large-scale integrated circuit.

Abstract: A superconducting device comprising a substrate having a principal surface, a non-superconducting oxide layer having a similar crystal structure to that of the oxide superconductor, a first and a second superconducting regions formed of c-axis oriented oxide superconductor thin films on the non-superconducting oxide layer separated from each other and gently inclining to each other, a third superconducting region formed of an extremely thin c-axis oriented oxide superconductor thin film between the first and the second superconducting regions, which is continuous to the first and the second superconducting regions.

Abstract: A Josephson junction is disclosed which includes a substrate of a single crystal having a substantially flat surface, a wiring pattern of an oxide superconductor formed on the flat surface of the substrate, and an altered region formed having a width of 300 nm or less and formed in the wiring pattern to intersect the wiring pattern, the crystal orientations of the wiring pattern on both sides of the altered region being equal to each other.

Abstract: A Josephson junction device comprising a single crystalline substrate including a principal surface, a layer of the same material as the substrate formed on the principal surface of the substrate so as to form a step on the principal surface, and an oxide superconductor thin film formed on the principal surface of the substrate. The oxide superconductor thin film includes a first and a second superconducting portions respectively positioned above and below the step, which are constituted of single crystals of the oxide superconductor, a junction portion between the first and the second superconducting portions, which is constituted of a single crystal of the oxide superconductor of which crystal orientation is different from those of the first and second superconducting portions, and grain boundaries between the first superconducting portion and the junction portion and between the second superconducting portion and the junction portion, which constitute one weak link of the Josephson junction.

Abstract: A superconducting device or a super-FET has a pair of superconducting electrode regions (20b,20c) consisting of a thin film (20)oxide superconductor being deposited on a substrate (5) and a weak link region (20a), the superconducting electrode regions (20b, 20c) being positioned at opposite sides of the weak link region (20a) these superconducting electrode regions (20b, 20c) and the weak link region (20a) being formed on a common plane surface of the substrate (5). The weak link region (20a) is produced by local diffusion of constituent element(s) of the substrate (5) into the thin film (20) of the oxide superconductor in such a manner that a substantial wall thickness of the thin film (20) of the oxide superconductor is reduced at the weak link region (20a) so as to leave a weak link or superconducting channel (10) in the thin film (20) of oxide superconductor over a non-superconducting region (50) which is produced by the diffusion.

Abstract: The invention relates to a method of manufacturing a superconducting device, which comprises the steps of forming on a principal surface of a substrate a non-superconducting oxide layer having a similar crystal structure to that of a c-axis oriented oxide superconductor thin film and a flat-top projection at its center portion, forming a c-axis oriented oxide superconductor thin film having an extremely thin thickness on the non-superconducting oxide layer so as to form a superconducting channel on the projecting portion of the non-superconducting oxide layer, forming an insulating layer on the c-axis oriented oxide superconductor thin film so as to form a gate insulating layer on the superconducting channel, and forming an a-axis oriented oxide superconductor thin film so as to form a superconducting source region and a superconducting drain region of which upper surfaces have the same level as that of the superconducting channel.

Abstract: A superconducting device comprising a substrate having a principal surface, a non-superconducting oxide layer having a similar crystal structure to that of the oxide superconductor, a first and a second superconducting regions formed of c-axis oriented oxide superconductor thin films on the non-superconducting oxide layer separated from each other and gently inclining to each other, a third superconducting region formed of an extremely thin c-axis oriented oxide superconductor thin film between the first and the second superconducting regions, which is continuous to the first and the second superconducting regions.

Abstract: A method of depositing high quality diamond films and a light emitting device are described. The deposition is carried out in a reaction chamber. After disposing a substrate to be coated in the chamber, a carbon compound gas including a C--OH bond is introduced together with hydrogen thereinto. Then, deposition of diamond takes place in a magnetic field by inputting microwave energy. The present invention is particularly characterized in that the volume ratio of the carbon compound to hydrogen introduced into the reaction chamber is 0.4 to 2; the pressure in said reaction chamber is 0.01 to 3 Torr; the temperature of the substrate is kept between 200.degree. to 1000.degree. C. during deposition; and the input energy of the microwave is no lower than 2 KW. By this method, uniform and high quality diamond films can be formed.

Abstract: A superconducting device has a substrate and a superconducting film formed on the substrate. A surface of the substrate has a first surface portion of which a curvature is constant or changes continuously, a second surface portion of which a curvature is constant or changes continuously, and a third surface portion at which the first and second surface portions meet and at which the curvatures of the first and second surface portions become discontinuous. The superconducting film formed on the surface of said substrate has a grain boundary serving as a junction only in a portion corresponding to the third surface portion of the substrate.

Abstract: A superconducting element includes a superconducting thin film bridge extending along the surface of a substrate, and a control electrode member for injecting quasi particles into a portion of an intersection region of the superconducting thin film bridge. The intersection region extends across the superconducting thin film bridge in a direction which is perpendicular to the current flow direction of the superconducting thin film bridge. A remaining portion of the intersection region, which is not injected with quasi particles by the control electrode member, operates as a weak-coupling bridge to thereby control the current flow within the superconducting thin film bridge.

Abstract: A superconducting device has a structure of superconductor--normal--conductor (semiconductor)--superconductor. The superconducting regions and the normal-conductor region can be made of the same elements but having different relative proportions of the elements. The device can be fabricated by introducing at least one element into an unmasked region of the superconductor to form a normal conductor region or into unmasked regions of the normal conductor to form superconductor regions.

Abstract: For manufacturing a superconducting device, a first oxide superconductor thin film having a very thin thickness is formed on a principal surface of a substrate, and a stacked structure of a gate insulator and a gate electrode is formed on a portion of the first oxide superconductor thin film. A second oxide superconductor thin film is grown on an exposed surface of the first oxide superconductor thin film, using the gate electrode as a mask, so that first and second superconducting regions having a relatively thick thickness are formed at opposite sides of the gate electrode, electrically isolated from the gate electrode. A source electrode and a drain electrode are formed on the first and second oxide superconducting regions. The superconducting device thus formed can function as a super-FET.

Abstract: Generally, and in one form of the invention, a microwave heterojunction bipolar transistor suitable for low-power, low-noise and high-power applications having an emitter 108, a base 126 and a collector 24 is disclosed, wherein the base 126 is composed of one or more islands 126 of semiconductor material. The one or more islands 126 are formed so that they do not cross any boundaries of the active area 60 of the transistor.Other devices, systems and methods are also disclosed.

Abstract: A superconducting device may include a superconducting weak link equipped with plural superconducting devices that are used as input-output terminals formed on the same plane and at least one current source for applying current to at least one of these superconducting electrodes. A superconducting device suitable for high integration can be realized as it enables structuring of a superconducting weak link 1 equipped with plural superconducting electrodes 101, 102, 103 and 104 that can be used as input-output terminals and changing symmetry of superconducting electrode arrangement through the form of a normal conductor 201 which is forming a superconducting weak link. In addition, when this superconducting device is used as a quasi-particle injection type device, a superconducting device with plural superconducting electrodes that can be used for a gate electrode, drain electrode or control electrode can be realized. Further, a superconducting device equipped with new functions (e.g.

Abstract: A SQUID comprises a substrate, a washer of an oxide superconductor thin film formed on a principal surface of the substrate, a hole shaped a similar figure to the washer at the center of the washer, a slit formed between one side of the washer and the hole, and a Josephson junction which connects portions of the washer at the both sides of the slit across the slit. In the SQUID, the ratio of similarity of the washer to the hole ranges 100 to 2500.

Abstract: A weak link is patterned from a high-temperature superconducting film using standard lithographic techniques. Once the area in which the weak link is to be located is defined, the remainder of the film is covered with an oxygen-impermeable material. The oxygen is then removed in the weak link area by placing the sample in a vacuum furnace at a sufficient temperature to drive out the oxygen. Once the oxygen is removed, the weak link becomes non-superconducting. A high power solid state laser is placed in front of the weak link, and superconductivity is restored in the weak link area, in situ. The process is performed in a liquid nitrogen environment.

Abstract: A superconducting thin film formed on a substrate, comprising an a-axis orientated oxide superconductor layer, a c-axis orientated oxide superconductor layer and an oxide semiconductor layer inserted between the a-axis orientated oxide superconductor layer and the c-axis orientated oxide superconductor layer, in contact with them in which superconducting current can flow between the a-axis orientated oxide superconductor layer and the c-axis orientated oxide superconductor layer through the oxide semiconductor layer by a long-range proximity effect.

Abstract: An oxide-superconducting device comprises first and second electrodes of oxide-superconductor which are connected through a tunnel barrier layer. The oxide-superconductor is formed on a substrate having a recess, and it includes grain boundaries along the recess. The tunnel barrier layer is formed along the grain boundaries, and it is made of any material of an element F, Cl, Br, I, C, O, S, P or N, a mixture consisting of such elements, and a compound containing such an element, the material being introduced into the grain boundaries and/or lattice interstices near the grain boundaries.

Abstract: A Josephson junction device comprising a single crystalline substrate including a principal surface having two horizontal planes and a smooth slope between the two horizontal planes, and an oxide superconductor thin film formed on the principal surface of the substrate. The oxide superconductor thin film includes a first and a second superconducting portions of a single crystalline oxide superconductor respectively positioned on the two horizontal planes of the substrate, a junction portion of a single crystalline oxide superconductor having a different crystal orientation from the two superconducting portions positioned on the slope of the substrate and two grain boundaries between each of the two superconducting portions and the junction portion. The grain boundaries constitutes one weak link of the Josephson junction.

Abstract: A superconducting transistor with superior withstand voltage having source region and a drain region formed of oxide superconductors 3, a PrBa.sub.2 Cu.sub.3 O.sub.7-x layer 2 or an ScBa.sub.2 Cu.sub.3 O.sub.7-x layer 2 forming an intermediate region sandwiched by the source and drain regions. The regions are disposed on a substrate 1. An insulation layer 4 is disposed on the intermediate region. A transistor uses the intermediate region as an insulator when the gate is turned off, and as a superconductor when the gate is turned on.

Abstract: A planar SQUID magnetometer for detection and measurement of an applied magnetic flux is disclosed wherein a planar microwave-resonant element overlaps a Josephson device incorporated in a high-T.sub.c superconducting, thin-film SQUID device, thereby providing inductive coupling between the planar microwave-resonant element and the SQUID device. When the microwave-resonant element is excited by incident high-frequency microwave radiation, the intensity of reflected microwave radiation varies in response to a magnetic flux applied to the SQUID device in accordance with non-linear oscillatory behavior of the microwave-resonant element due to inductive loading by the SQUID device. The microwave-resonant element and the SQUID device are preferably fabricated photolithographically on a single substrate.

Abstract: The invention relates to a structured superconductive track and a process for making it from epitaxial high temperature superconductor (HTSC) layers using lift off technique, in which a HTSC track deposited on an elevated substrate region is surrounded by an insulating layer of doped HTSC lying on a lower substrate region, and the substrate region with the superconductive track formed thereon is elevated such that the superconductive track is isolated from the insulating layer.

Abstract: A superconducting device comprises a substrate having a principal surface and a non-superconducting oxide layer having a similar crystal structure to that of the oxide superconductor, which has a projection at its center portion. A superconducting source region and a superconducting drain region formed of an .alpha.-axis oriented oxide superconductor thin film are positioned at the both sides of the projection of the non-superconducting oxide layer separated from each other and an extremely thin superconducting channel formed of a c-axis oriented oxide superconductor thin film is positioned on the projection of the non-superconducting oxide layer. The superconducting channel electrically connects the superconducting source region to the superconducting drain region, so that superconducting current can flow through the superconducting channel between the superconducting source region and the superconducting drain region.

Abstract: A process for producing a Josephson device is disclosed, wherein a Josephson junction is formed over a recess step by oblique deposition and a protective layer of conducting material or semiconducting material is formed on the Josephson junction. The actual thickness of the Josephson junction is controlled to be smaller due to the proximity effect.

Abstract: This field-effect transistor comprises a conductive substrate (2) serving as the gate electrode, an insulating barrier layer (3), and a superconducting channel layer (1) on top of the barrier layer (3). The superconductor layer (1) carries a pair of mutually spaced electrodes (4, 5) forming source and drain, respectively. The substrate is provided with an appropriate gate contact (6).The substrate (2) consists of a material belonging to the same crystallographic family as the barrier layer (3). In a preferred embodiment, the substrate (2) is niobium-doped strontium titanate, the barrier layer (3) is undoped strontium titanate, and the superconductor (1) is a thin film of a material having a lattice constant at least approximately similar to the one of the materials of the substrate (2) and barrier (3) layers. A preferred material of this type is YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where 0.ltoreq..delta..ltoreq.0.5.

Abstract: A microbridge superconductor device includes a substrate, made of a material such as LaAlO.sub.3, having a lower planar substrate surface, an inclined surface having an overall upward inclination of from about 20 to about 80 degrees from the plane of the lower planar substrate surface, and an upper planar substrate surface parallel to the lower planar substrate surface and separated from the lower planar substrate surface by the inclined surface. A layer of a c-axis oriented superconductor material, made of a material such as YBa.sub.2 Cu.sub.3 O.sub.7-x, is epitaxially deposited on the lower planar substrate surface, and has an exposed a-axis edge adjacent the intersection of the lower planar substrate surface with the inclined surface. The a-axis exposed edge is beveled away from the intersection. A layer of a c-axis oriented superconductor material is epitaxially deposited on the upper planar substrate surface, and has an exposed a-axis edge adjacent the inclined surface.

Abstract: A magnetic flux-enhanced control line for a superconducting flux flow transistor (SFFT). The SFFT includes a pair of superconducting electrodes which provide a voltage output, a region of weakened superconductor connecting the electrodes and a control line. The region of weakened superconductor carries a current I.sub.body and the control line carries a current I.sub.Control. The control line further has a portion thereof proximate the weakened region for providing a localized magnetic field through the weakened region as a function of I.sub.Control. The magnetic flux through the weakened region induces vortices therein which have a resistance r.sub.o. The proximate portion of the control line forms a tortuous current path whereby the magnetic flux through the weakened region is increased for increasing r.sub.o so that the output voltage of the transistor is increased without increasing I.sub.Control.

Abstract: A superconducting device has a structure of superconductor - normal-conductor (semiconductor) - superconductor. The superconductors constituting the superconducting device are made of a superconducting oxide material of K.sub.2 NiF.sub.4 type crystal-line structure or perovskite type crystalline structure which contains at least one element selected from the group consisting of Ba, Sr, Ca, Mg and Ra; at least one element selected from the group consisting of La, Y, Ce, Sc, Sm, Eu, Er, Gd, Ho, Yb, Nd, Pr, Lu and Tb; Cu; and O.

Abstract: A superconducting field effect transistor which is very small in size and high in dimensional accuracy, has a first layer of material forming a control electrode and a second layer of another material is disposed on said first layer. A width of said first layer in a direction toward a superconducting source electrode and a superconducting drain electrode is narrower than a width of the second layer in the same direction. Polycrystalline silicon may be used as the control electrode while the second layer can be made of silicon nitride. Furthermore, a side surface of the control electrode may be coated with an insulator film. Accordingly, the above transistor has a fine structure gate electrode part that can be fabricated easily and accurately.

Abstract: In a Josephson device which can be employed as a sensor including superconductor for measuring an extremely weak magnetic field, a Josephson junction consisting of superconducting material is formed, and a covering layer consisting of ordinary conducting metal or semiconductor is formed on the Josephson junction. This enables the Josephson junction to be isolated from the oxidized atmosphere. Further, the covering layer is not to present any deterioration such as cracks even upon being subjected to a thermal hysteresis from very low temperature to ordinary temperature.

Abstract: Superconducting electrodes are formed on a semiconductor which serves as a channel. A control electrode is disposed through an insulator film or a p-n junction on the side of the semiconductor which is opposite to the semiconductor side on which the superconducting electrode is formed. A superconducting current flows between the superconducting electrode across the semiconductor is controlled by an electric signal which is applied to the control electrode, thereby enhancing the current gain.

Abstract: A method is disclosed for fabricating grain boundary junction devices, which comprises preparing a crystalline substrate containing at least one grain boundary therein, epitaxially depositing a high Tc superconducting layer on the substrate, patterning the superconducting layer to leave at least two superconducting regions on either side of the grain boundary and making electrical contacts to the superconducting regions so that bias currents can be produced across the grain boundary.

Abstract: In a superconducting device wherein the value of a superconducting current to flow between two superconducting electrodes provided in contact with a semiconductor is controlled by a control electrode provided between the superconducting electrodes, high impurity concentration regions are formed within the semiconductor so as to lie in contact with the superconducting electrodes and to extend to under ends of the control electrode.

Abstract: An oxide superconducting device has a junction structure composed of at least one oxide superconductor and at least one insulator in which carriers have been generated. As the insulator in which carriers have been generated, there can be used, for example, SrTiO.sub.3 doped with Nb. With such a device, rectifying characteristics can be attained in the junction.

Abstract: A tunnel junction type superconducting device includes a pair of superconductor electrodes formed of compound oxide superconductor material, and a metal layer of a high electric conductivity formed between the pair of superconductor electrodes so as to maintain the pair of superconductor electrodes separate from each other. The pair of superconductor electrodes is separated from each other by a distance within a range of 3 nm to 70 nm by action of the metal layer.

Abstract: A superconducting device includes a superconducting channel consituted of an oxide superconductor thin film formed on a substrate, a superconductor source electrode and a superconductor drain electrode formed at opposite ends of the superconducting channel, so that a superconducting current can flow through the superconducting channel between the source electrode and the drain electrode. A gate electrode is located through an insulating layer on the superconducting channel so as to control the superconducting current flowing through the superconducting channel. The oxide superconductor thin film of the superconducting channel is formed of a c-axis oriented oxide superconductor crystal, and the oxide superconductor thin film of the superconductor source electrode and the superconductor drain electrode are formed of an a-axis oriented oxide superconductor crystal. The superconducting channel is continuous with the superconductor source electrode and the superconductor drain electrode.

Abstract: A superconducting device has a structure of superconductor - normal-conductor (semiconductor) - superconductor. The superconductors constituting the superconducting device are made of a super-conducting oxide material of K.sub.2 NiF.sub.4 type crystalline structure or perovskite type crystalline structure which contains at least one element selected from the group consisting of Ba, Sr, Ca, Mg and Ra; at least one element selected from the group consisting of La, Y, Ce, Sc, Sm, Eu, Er, Gd, Ho, Yb, Nd, Pr, Lu and Tb; Cu; and O.

Abstract: In a dc SQUID element having two quasi-planar-type Josephson junction portions, as obtained by laminating a plurality of superconducting thin films on a substrate, a SQUID ring and a counter electrode on either of which quasi-planar-type Josephson junction portions are to be formed, are respectively formed at the lowermost layer and the uppermost layer, or at the uppermost layer and the lowermost layer, so that the value of critical current can be adjusted. The arrangement above-mentioned assures good flatness and film quality of a barrier layer interposed between the lower and upper electrodes of the quasi-planar-type Josephson junction portions.

Abstract: An oxide-superconducting device comprises first and second electrodes of oxide-superconductor which are connected through a tunnel barrier layer. The oxide-superconductor is formed on a substrate having a recess, and it includes grain boundaries along the recess. The tunnel barrier layer is formed along the grain boundaries, and it is made of any material of an element F, Cl, Br, I, C, O, S, P or N, a mixture consisting of such elements, and a compound containing such an element, the material being introduced into the grain boundaries and/or lattice interstices near the grain boundaries.

Abstract: A transistor structure which utilizes the Josephson effect and/or tunneling effect. The Josephson transistors of the invention are composed of superconductive films and tunneling films and work at a high speed with a low energy consumption. They are suitable for the construction of integrated circuits, especially digital circuits.

Abstract: High T.sub.c superconducting devices are described in which controlled grain boundaries in a layer of the superconductors forms a weak link or barrier between superconducting grains of the layer. A method is described for reproducibly fabricating these devices, including first preparing a substrate to include at least one grain boundary therein. A high T.sub.c superconductor layer is then epitaxially deposited on the substrate in order to produce a corresponding grain boundary in the superconducting layer. This superconducting layer is then patterned to leave at least two regions on either side of the grain boundary, the two regions functioning as contact areas for a barrier device including the grain boundary as a current flow barrier. Electrical contacts can be made to the superconducting regions so that bias currents can be produced across the grain boundary which acts as a tunnel barrier or weak link connection.