Proximity coupling in high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">T</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Josephson junctions produced by focused electron beam irradiation

Booij, W.E.; Pauza, Andrew; Tarte, E.J.; Moore, David F.; Blamire, M. G.

doi:10.1103/physrevb.55.14600

Cited by 51 publications

(30 citation statements)

References 18 publications

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“…Critical current (µA) cm behavior is consistent with existing models of superconductor normal superconductor (SNS) junctions with soft boundary conditions [6,9].…”

Section: (A)supporting

confidence: 58%

Nanometer scale masked ion damage barriers in YBa/sub 2/Cu/sub 3/O/sub 7-δ/

Kang

Speaks

Peng

et al. 2001

IEEE Trans. Appl. Supercond.

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“…Critical current (µA) cm behavior is consistent with existing models of superconductor normal superconductor (SNS) junctions with soft boundary conditions [6,9].…”

Section: (A)supporting

confidence: 58%

Nanometer scale masked ion damage barriers in YBa/sub 2/Cu/sub 3/O/sub 7-δ/

Kang

Speaks

Peng

et al. 2001

IEEE Trans. Appl. Supercond.

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“…1, we also show the dependence of the critical current on the external magnetic field from 21 K to 33 K; the crossover from a minimum to a maximum zero-field critical current between T=24.7 K and T=27.8 K is consistent with the T* value extrapolated by I-V characteristics and strong evidence that one of the two single junctions undergoes a 0-π phase transition close to T* [11]. 3 Bilayer SNS junctions The desirable feature of grain boundary junctions in HTS and their extension, junctions formed by electron-beam [12] and ion irradiation [13], is that junctions can be fabricated from deposited films with only a single lithographic process. We have developed processes which allow these features to be extended to low temperature superconductor (LTS).…”

Section: Hts Grain Boundary Devicessupporting

confidence: 76%

Focused ion beam fabrication and properties of nanoscale Josephson junctions for sensors and other applications

Blamire

Bell

Burnell

et al. 2005

phys. stat. sol. (c)

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PACS 74.50.+r, 74.81.Fa, 85.25.Cp, The methods of superconducting device fabrication by lithography and multilevel processing usually require a number of processing steps with lithographic resolution and alignment adequate for the scale of the device be fabricated. As an alternative, the focused ion beam (FIB) microscope is increasingly being used directly to fabricate devices. A major advantage of using a FIB compared to other lithography methods is its flexibility and high resolution. It allows in-situ, milling (~5 nm at a beam current of 1 pA) to a variety of depths, and imaging (2 nm) of the sample. In this paper we describe our development of junction fabrication techniques using the FIB and their application in creating a range of potential sensor devices and quantum electronics applications.1 Introduction Focused ion beam (FIB) systems offer the ease of use of a scanning electron microscope (SEM) but with sectioning and cross-sectional imaging capabilities which SEMs lack. Historically, their development was driven by the semiconductor production industry but their increasing availability within research institutions has enabled the development of new applications making widespread the use and development of these techniques.In a typical FIB system a focused ion-beam ejected from a liquid metal ion source (usually Ga), with a spot size of less than 10 nm, is scanned across a sample in a manner analogous to a SEM. Imaging using secondary electrons provides surface information with similar resolution to that obtainable from an SEM; however the main applications arise from the use of ions as the scanned species. These include compositional imaging via secondary ions, direct etching of material in selected regions for in-situ sectioning and imaging, microfabrication, transmission electron microscopy specimen preparation, and localised deposition and implantation of metal and insulator structures. The unique combination of 10 nm resolution imaging with the ability both to remove and to deposit material in selected areas provides a means of performing experiments which would otherwise be impossible or unreasonably timeconsuming.At its most general, a Josephson junction consists of two superconducting electrodes separated by a weak-link in which superconductivity is eliminated or suppressed: for example by an insulating tunnel barrier in a superconductor -insulator -superconductor (SIS) junction or by a thin non-superconducting metal layer in a superconductor -normal -superconductor (SNS) junction. All Josephson junctions for

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“…If we take the modal value of ∆ reported in the literature (5meV) [6][7][8][9] , I C R N for the MgB 2 junction is close to the direct prediction of de Gennes, 24 whereas for the YBa 2 Cu 3 O 7-d junctions it is much lower, implying strong gap suppression in the electrodes. 25 Direct calculation of ξ ND ( (hv f l / (4πkT c )) 0.5 ) is difficult given the uncertainty of the mean-free path (l), but using a value of 4.7x10 5 for the Fermi velocity (v f ) 2 , our value for ξ ND implies that l is of the order of 5nm. A value of 60nm for polycrystalline superconducting MgB 2 has been deduced previously, so this value does not seem unreasonable if the ion damage strongly reduces the carrier density in the barrier.…”

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confidence: 99%

Planar superconductor-normal-superconductor Josephson junctions in MgB2

Burnell

Kang

Lee³

et al. 2001

Applied Physics Letters

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Since the discovery of superconductivity in MgB 2 1 considerable progress has been made in determining the physical properties of the material, which are promising for bulk conductors 2-5 . Tunneling studies [6][7][8][9] show that the material is reasonably isotropic and has a well-developed s-wave energy gap (∆), implying that electronic devices based on MgB 2 could operate close to 30K. Although a number of groups have reported the formation of thin films by post-reaction of precursors 10-14 , heterostructure growth is likely to require considerable technological development, making single-layer device structures of most immediate interest. MgB 2 is unlike the cuprate superconductors in that grain boundaries do not form good Josephson junctions, and although a SQUID based on MgB 2 nanobridges has been fabricated 15 , the nanobridges themselves do not show junction-like properties. Here we report the successful creation of planar MgB 2 junctions by localised ion damage in thin films. The critical current (I C ) of these devices is strongly modulated by applied microwave radiation and magnetic field. The product of the critical current and normal state resistance (I C R N ) is remarkably high, implying a potential for very high frequency applications.Our film deposition technique has been described elsewhere. 12 Briefly, B films were deposited at room temperature on to (0001) sapphire substrates by electron beam evaporation and then ex-situ annealed in a Mg vapour at 850°C for 30 minutes to produce MgB 2 films with a final thickness of 100nm and a critical temperature (T C ) of 36K. We deposited a 20nm Au film onto the films by dc magnetron sputtering in order to protect the MgB 2 from contact with water during subsequent processing. Tracks and contact pads were patterned in the bilayer film using standard photolithography and broad beam Ar-ion milling. The T C of the patterned tracks was approximately 35K. In order to fabricate the junctions, the film was then transferred to a focused ion beam system (FIB) (Philips-FEI Inc. FIB 200). Chips were wirebonded to enable the resistance of the tracks to be monitored during the FIB milling process. 16 The barrier was defined by writing 50nm wide cuts across the width of tracks using a 4pA 30kV Ga ion beam. The depth of the cut was calibrated by comparing the cut time to that required to completely sever a track; since the Au mills more than order of magnitude faster than the MgB 2 it could be ignored in calibrating the cut depth. Compared to other materials used to fabricate SNS junctions using this technique, 17 MgB 2 offers the advantage of a relatively low milling rate and hence excellent depth control due to the low atomic mass of its constituents and high melting point.The devices were measured in dip probes placed in 4 He storage dewars. The probes are equipped with coils to provide a magnetic field perpendicular to the substrate plane, and with a microwave antenna. The inset to Fig. 1 shows the resistance against temperature for two tracks on the same substrate,...

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Proximity coupling in high-TcJosephson junctions produced by focused electron beam irradiation

Cited by 51 publications

References 18 publications

Nanometer scale masked ion damage barriers in YBa/sub 2/Cu/sub 3/O/sub 7-δ/

Nanometer scale masked ion damage barriers in YBa/sub 2/Cu/sub 3/O/sub 7-δ/

Focused ion beam fabrication and properties of nanoscale Josephson junctions for sensors and other applications

Planar superconductor-normal-superconductor Josephson junctions in MgB2

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