Josephson junction array device, and manufacture thereof

Abstract

A superconductive device is disclosed, which has specific characteristics of a generator and/or detector of sub-millimeter wavelength radiation, comprising a two-dimensional lateral array of mesas (column-shaped elements) each containing vertically stacked Josephson junctions on top of one another. This device is capable of covering the entire frequency range between the microwave and far infrared spectral regions, in a plurality of applications, where radiation emission and detection is involved. According to its various embodiments, thin columns (stacks) of Josephson junctions are monolithically built between superconducting electrical top and bottom contact layers. Mutually isolated segments cut out of the contact layers allow for optimization of circuit parameters such as impedance matching to load and maximizing the output power. External electronic control allows modulation of the radiation field and other operation modes of the device. The specification also describes special applications of the disclosed device.

1 . A Josephson junction array device, comprised of a substrate, a superconducting thin film, deposited on that substrate and containing a sequence of layers typical in a series array of vertically stacked Josephson junctions, comprising further a superconducting mesa structure or structures on top of, or fabricated out of said superconducting thin film, electrical bottom and top contacts and means for applying an electrical voltage or current to the electrodes, characterised in that the mesas are monolithically integrated between superconducting electrical end contacts on either side, and that means are provided for any partial number of those superconducting mesas being combined in groups for interconnection and control purposes.  
     
     
         2 . A Josephson junction array device according to    claim 1   , accomplished in epitaxially grown c-axis oriented high-T c  superconductor films containing intrinsic Josephson junction stacks.  
     
     
         3 . A Josephson junction array device according to    claim 1   , with artificially fabricated Josephson junction stacks, achieved by inserting barrier layers between high-T c  superconductor layers that serve as superconducting electrodes.  
     
     
         4 . A Josephson junction array device according to    claim 1   , where barrier layers are created by site-selective doping which reduces the critical temperature of high-T c  superconductor materials.  
     
     
         5 . A Josephson junction array device according to    claim 1   , fabricated in a high-T c  superconductor single crystal which contains intrinsic Josephson junction stacks.  
     
     
         6 . A Josephson junction array device according to    claim 1   , accomplished in a superconducting metal-insulator-metal superlattice structure, where each metal-insulator-metal unit is designed to provide for the properties of a Josephson junction.  
     
     
         7 . The method of producing a Josephson junction array device as defined in    claims 1    to    6   , wherein the superconducting multilayer film is epitaxially grown by Molecular Beam Epitaxy (MBE) and its analogues, as e.g., Atomic Layer Epitaxy (ALE), Fine-focus Ion Beam Epitaxy (FIBE), etc.  
     
     
         8 . The method of producing a Josephson junction array device as defined in    claim 7   , where the MBE-apparatus is provided with spectroscopic means for interface inspection and control of the growing films.  
     
     
         9 . A method of forming a Josephson junction array device according to claims  2 ,  3 , and  7 , comprising the following steps 
 (a) epitaxially grow a high-T c  superconductor film, about 100-200 nm thick, on a suitable wafer,    (b) cool down and deposit a protective overlayer, 1-10 nm thick, on top of the high-T c  superconductor-film,    (c) apply lithography for array definition on the overlayer, and ion-mill through the overlayer and about halfway through the deposited high-T c  superconductor film,    (d) deposit an insulating film, and dissolve the photoresist on top of the mesas,    (e) apply a temperature cycle, and lift off the protective overlayer in order to recreate the pristine top surface of the columns (mesas),    (f) deposit a second high-T c  superconductor film on top of the whole upper surface for top-contact definition,    (g) deposit metal contacts on the top and the bottom high-T c  superconductor electrodes.    
     
     
         10 . A method for manufacturing a Josephson junction array device according to    claim 9   , with additional fabrication of parallel superconducting contacts between linear Josephson junction arrays in mesa structures, comprised of the following steps: 
 (a) deposit the first high-T c  superconductor film (HTS-1) and the protective overlayer,    (b) spin-on, expose, and develop the photoresist for mesa etch,    (c) etch or ion-mill to define mesa structures,    (d) deposit the insulator,    (e) dissolve the photoresist and lift-off the insulator above it,    (f) remove the protective overlayer by evaporation within the growth chamber,    (g) deposit the second high-T c  superconductor layer (HTS-2),    (h) spin-on, expose, and develop photoresist for the segment definition-etch,    (i) etch or ion-mill to define the cluster structure,    (j) dissolve photoresist,    (k) deposit metal contacts on the top and the bottom high-T c  superconductor electrodes.    
     
     
         11 . A method of manufacturing a Josephson junction array device according to    claim 10   , which enables the fabrication of both series connections of mesas and parallel connections of mesas, comprised of the following steps: 
 (a) deposit the first high-T c  superconductor (HTS-1) and protective overlayer, etch to define mesas, deposit insulator, and remove photoresist,    (b) etch away to form the trench separating the two clusters, deposit insulator, and remove photoresist,    (c) remove the protective overlayer and deposit the second high-T c  superconductor layer (HTS-2),    (d) spin-on photoresist, align carefully, expose, develop, and etch the trenches in the high-T c  superconductor (HTS-2) layer to separate the segments,    (e) deposit metal contacts on the top and the bottom high-T c  superconductor electrodes.    
     
     
         12 . A method of manufacturing a Josephson junction array device according to claims  6  and  7 , which is comprised of the following steps: 
 (a) epitaxially grow a first metal film (M), at least one superconducting coherence length thick,  
 (b) epitaxially create a thin insulator (I) on top of first metal film,  
 (c) epitaxially grow a second metal film, at least one super conducting coherence length thick, on top of the insulator,  
 (d) epitaxially grow a second thin insulator on top of the second metal film, and repeat (a) through (d) 2-100 times,  
 (e) deposit a protective overlayer,  
 (f) apply lithography for array definition on the uppermost layer, and ion-mill through the overlayer and halfway through the deposited MIM-structure,  
 (g) deposit an insulator film, and dissolve the photoresist on top of the mesas,  
 (e) apply a temperature cycle, and lit off the protective overlayer in order to recreate the pristine top surface of the columns (mesas),  
 (f) deposit a thick metal layer on top of the crystalline columns for top-contact definition.  
 
     
     
         13 . A method of producing a Josephson junction array device as claimed in any of the    claims 1    to    6   , wherein the superconducting multilayer film is epitaxially grown by Chemical Vapor Deposition (CVD) and its analogues.  
     
     
         14 . A method of producing a Josephson junction array device as claimed in any of the    claims 1    to    6   , wherein the superconducting layer system is grown by Pulsed Laser Deposition (PLD) and its analogues.  
     
     
         15 . A method of producing a Josephson junction array device as claimed in    claim 14   , where the PLD apparatus is provided with spectroscopic means for interface inspection and control of the growing films.  
     
     
         16 . A method of producing a Josephson junction array device as claimed in any of the    claims 1    to    6   , wherein the superconducting layer system is grown by Sputter Deposition (SD) and its analogues.  
     
     
         17 . A method of producing a Josephson junction array device as claimed in    claim 16   , where the SD apparatus is provided with spectroscopic means for the control of the growing films.  
     
     
         18 . A method of producing a Josephson junction array device as claimed in any of the    claims 1    to    6   , wherein the high-T c  superconductor is grown as a bulk single crystal material.  
     
     
         19 . A method of producing a Josephson junction array device as claimed in any of the    claims 1    to    6   , where the device is fabricated by use of of an array-defining micro-mask.  
     
     
         20 . A Josephson junction array device as claimed in any of the    claims 1    to    6   , comprising a linear or two-dimensional lateral array of at least 2 to several thousand columns in parallel connection, each of said columns containing 2 to 2000 vertically stacked Josephson junctions, between common superconducting base and top contacts, with means for connecting to a controllable current source such that the Josephson junctions are driven into the ac (emitting) regime.  
     
     
         21 . A Josephson junction array device according to    claim 20   , where the contact means provide for voltage measurements in the detector regime.  
     
     
         22 . A Josephson junction array device according to    claim 20   , comprising superconducting top contacts split into two segments, with means for connecting to a controllable current source such that a series connection between the two segments, each containing multiple parallel connected columns, is achieved.  
     
     
         23 . A Josephson junction array device according to    claim 20   , where the top contact is split in three or more segments with means for connecting to a controllable current source such that a series connection of three or more segments with parallel connected columns is achieved.  
     
     
         24 . A Josephson junction array device according to claims  20 ,  21 , and  23 , where any available segment is accessible independently by external means in order to affect or suppress the ac (emitting) regime of certain segments.  
     
     
         25 . A Josephson junction array device according to claims  20 ,  21  and  24 , where any available segment is accessible independently by external means in order to establish an integrated detector mode of certain segments in parallel with the ac (emitting) regime of other segments.  
     
     
         26 . A Josephson junction array device according to    claim 23   , where a distributed array of series connected Tunneltron segments is formed, placed at wavelength intervals along a serpentine microstrip transmission line for higher power output.  
     
     
         27 . An emitter and/or a detector (sensor) of electromagnetic radiation in the millimeter and sub-millimeter spectral region for communication and data transfer purposes based on the Josephson junction array device according to any of the preceding claims.  
     
     
         28 . A monolithic emitter-detector device of electromagnetic radiation for radar-applications, including panoramic observations, based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         29 . An emitter and detector device with focus-shifting wave field properties (to be used, for example, in holographic imaging) based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         30 . An emitter device with beam sweeping properties for addressing spatially separated receptors or deflectors, based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         31 . An emitter and detector device applied for satellite-based synthetic aperture radar (SAR) based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         32 . A monolithic emitter-detector device for millimeter and sub-millimeter electromagnetic radiation for multi-frequency imaging microwave radiometer applications based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         33 . An emitter and detector device of electromagnetic radiation in the millimeter and sub-millimeter spectral region used for coding and enciphering by means of the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         34 . An emitter and detector device applied for a microwave spectrometer based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .  
     
     
         35 . An emitter device utilized as local oscillator in a heterodyne mixer for astronomical exploration apparatus, based on the Josephson junction array device as claimed in any of the    claims 1    to    26   .