Hydrogenated amorphous silicon barriers for niobium-niobium Josephson junctions

Kröger, H.; Smith, L. N.; Jillie, D. W.; Thaxter, J. B.; Aucoin, Richard; Currier, L.W.; Potter, C.N.; Shaw, D. M.; Willis, Peter

doi:10.1109/tmag.1985.1063748

Cited by 12 publications

(4 citation statements)

References 15 publications

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“…Among devices with direct conduction, relatively high values of V c required for digital applications have been demonstrated by Nb-based junctions with amorphous Si barriers doped by various impurities creating deep levels near the middle of the band gap, like Nb, W, etc. ; see [128] and references therein, [129-[131], and many older works, e.g., [132]- [134]. From the author's point of view, their only advantage is that, at large levels of doping (~ 10%), selfshunting and nonhysteretic behavior is obtained.…”

Section: Vlsi Technology Developmentmentioning

confidence: 99%

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Tolpygo¹

2016

Low Temperature Physics

178

115

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Abstract-Superconductor digital electronics using Josephson junctions as ultrafast switches and magnetic-flux encoding of information was proposed over 30 years ago as a sub-terahertz clock frequency alternative to semiconductor electronics based on complementary metal-oxide-semiconductor (CMOS) transistors. Recently, interest in developing superconductor electronics has been renewed due to a search for energy saving solutions in applications related to high-performance computing. The current state of superconductor electronics and fabrication processes are reviewed in order to evaluate whether this electronics is scalable to a very large scale integration (VLSI) required to achieve computation complexities comparable to CMOS processors. A fully planarized process at MIT Lincoln Laboratory, perhaps the most advanced process developed so far for superconductor electronics, is used as an example. The process has nine superconducting layers: eight Nb wiring layers with the minimum feature size of 350 nm, and a thin superconducting layer for making compact high-kineticinductance bias inductors. All circuit layers are fully planarized using chemical mechanical planarization (CMP) of SiO 2 interlayer dielectric. The physical limitations imposed on the circuit density by Josephson junctions, circuit inductors, shunt and bias resistors, etc., are discussed. Energy dissipation in superconducting circuits is also reviewed in order to estimate whether this technology, which requires cryogenic refrigeration, can be energy efficient. Fabrication process development required for increasing the density of superconductor digital circuits by a factor of ten and achieving densities above 10 7 Josephson junctions per cm 2 is described.

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Section: Vlsi Technology Developmentmentioning

confidence: 99%

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Tolpygo¹

2016

Low Temperature Physics

178

115

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“…The Appelbaum-Anderson model has been successfully applied to Josephson tunnel junctions formed by low-temperature superconductors employing hydrogenated amorphous silicon barriers [29]. Initially, it also was used to explain the experimentally observed zero bias conductance peak in tunnel junctions employing HTS electrodes [12,30,31,32,33,34].…”

Section: Appelbaum-anderson Modelmentioning

confidence: 99%

Andreev bound states in high temperature superconductors

et al. 1998

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Abstract. Andreev bound states at the surface of superconductors are expected for any pair potential showing a sign change in different k-directions with their spectral weight depending on the relative orientation of the surface and the pair potential. We report on the observation of Andreev bound states in high temperature superconductors (HTS) employing tunneling spectroscopy on bicrystal grain boundary Josephson junctions (GBJs). The tunneling spectra were studied as a function of temperature and applied magnetic field. The tunneling spectra of GBJ formed by YBa2Cu3O 7−δ (YBCO), Bi2Sr2CaCu2O 8+δ (BSCCO), and La1.85Sr0.15CuO4 (LSCO) show a pronounced zero bias conductance peak that can be interpreted in terms of Andreev bound states at zero energy that are expected at the surface of HTS having a d-wave symmetry of the order parameter. In contrast, for the most likely s-wave HTS Nd1.85Ce0.15CuO4−y (NCCO) no zero bias conductance peak was observed. Applying a magnetic field results in a shift of spectral weight from zero to finite energy. This shift is found to depend nonlinearly on the applied magnetic field. Further consequences of the Andreev bound states are discussed and experimental evidence for anomalous Meissner currents is presented.

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“…The present paper is devoted to the detailed investigation of the effects of the PECVD process on the superconducting, normal-state and structural properties of a 20 nm thick Nb film which was utilized as a substrate for the a-Si:H growth. Nitridation of Nb films [9] and deposition of a sputtered thin amorphous unhydrogenated Si layer on the Nb films [10] (in both cases made in situ after Nb film deposition) were investigated as methods for protecting the Nb films during PECVD. As regards the latter protective method, in [10] a thin (0.8-0.9 nm) amorphous unhydrogenated Si layer has already been utilized for protection of the Nb base electrode from hydrogen diffusion during the deposition of a thin (4 nm) a-Si:H layer as a tunnel barrier made by RF sputtering of a Si target in an Ar/H 2 mixture atmosphere at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Nitridation of Nb films [9] and deposition of a sputtered thin amorphous unhydrogenated Si layer on the Nb films [10] (in both cases made in situ after Nb film deposition) were investigated as methods for protecting the Nb films during PECVD. As regards the latter protective method, in [10] a thin (0.8-0.9 nm) amorphous unhydrogenated Si layer has already been utilized for protection of the Nb base electrode from hydrogen diffusion during the deposition of a thin (4 nm) a-Si:H layer as a tunnel barrier made by RF sputtering of a Si target in an Ar/H 2 mixture atmosphere at room temperature. In contrast, in the present work the protective capability of the thin (3 nm) amorphous unhydrogenated Si layer has been investigated in detail in the case of thick (∼250 nm) a-Si:H deposited on an Nb film by a PECVD process at high temperature (in our experiment, 250 • C).…”

Section: Introductionmentioning

confidence: 99%

Superconducting and structural properties of Nb films covered by plasma enhanced chemical vapor deposited a-Si:H layers for superconducting qubit application

Bruno

Mengucci

Mercaldo

et al. 2013

Supercond. Sci. Technol.

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With a view to the fabrication of superconducting qubits with low decoherence time, we have investigated the influence of a-Si:H deposition by the plasma enhanced chemical vapor deposition method at 250 • C on the superconducting and structural properties of a 20 nm thick Nb film treated by two surface protection methods: plasma nitridation and deposition of a thin unhydrogenated Si layer. A suppression of the T c and an increase of the residual resistivity are observed due to hydrogen diffusion and decomposition of the native surface oxide, with subsequent oxygen diffusion caused by sample heating. The unhydrogenated Si layer is found to efficiently protect the Nb films against both diffusion processes.

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Hydrogenated amorphous silicon barriers for niobium-niobium Josephson junctions

Cited by 12 publications

References 15 publications

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Andreev bound states in high temperature superconductors

Superconducting and structural properties of Nb films covered by plasma enhanced chemical vapor deposited a-Si:H layers for superconducting qubit application

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