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Structure and Transport Characteristics of Tunnel Junctions with Hybrid Semiconductor Barriers with Quantum Dots

100%

Shaternik V., Shapovalov A., Prikhna T., Suvorov O., Skorik M., Shaternik A., Bondarchuk V., Zubov E.

Acta Physica Polonica A

2018

vol. 133

issue 4

1060-1064

We propose to realize MoRe/SiO_x(W)/MoRe hybrid junctions by using self-organization effects for the creation of quantum dots (tungsten clusters) in the semiconductor barriers consisting of a mixture of silicon and silicon oxide. Current-voltage characteristics of the MoRe/SiO_x(W)/MoRe samples have been measured in a wide voltage range from -900 to 900 mV at temperatures from 4.2 to 77 K. At low temperatures and for a comparatively small W content in the hybrid barrier, the heterostructures exhibited current-voltage curves of an unusual shape. Single or several current peaks caused by electron tunneling through the allowed states in the barrier have been observed in the transport characteristics. With increasing temperature, superconducting fluctuations in the MoRe electrodes become unimportant, and the current-voltage curve of a heterostructure follows the Ohm law. At last, we present theoretical description of the charge transport in such inhomogeneous systems with account of many-electron processes.

Nanostructural Superconducting Materials for Fault Current Limiters and Cryogenic Electrical Machines

53%

Prikhna T., Gawalek W., Savchuk Y., Sergienko N., Moshchil V., Sokolovsky V., Vajda J., Tkach V., Karau F., Weber H., Eisterer M., Joulain A., Rabier J., Chaud X., Wendt M., Dellith J., Danilenko N., Habisreuther T., Dub S., Meerovich V., Litzkendorf D., Nagorny P., Kovalev L., Schmidt C., Melnikov V., Shapovalov A., Kozyrev A., Sverdun V., Kosa J., Vlasenko A.

issue 1

7-14

Materials of the Y-Ba-Cu-O (melt-textured YBa_{2}Cu_{3}O_{7-δ}-based materials or MT-YBCO) and Mg-B-O (MgB_{2}-based materials) systems with high superconducting performance, which can be attained due to the formation of regularly distributed nanostructural defects and inhomogeneities in their structure can be effectively used in cryogenic technique, in particular in fault current limiters and electrical machines (electromotors, generators, pumps for liquid gases, etc.). The developed processes of high-temperature (900-800°C) oxygenation under elevated pressure (16 MPa) of MT-YBCO and high-pressure (2 GPa) synthesis of MgB_{2}-based materials allowed us to attain high superconductive (critical current densities, upper critical fields, fields of irreversibility, trapped magnetic fields) and mechanical (hardness, fracture toughness, Young modulus) characteristics. It has been shown that the effect of materials properties improvement in the case of MT-YBCO was attained due to the formation of high twin density (20-22 μm^{-1}), prevention of macrocracking and reduction (by a factor of 4.5) of microcrack density, and in the case of MgB_{2}-based materials due to the formation of oxygen-enriched as compared to the matrix phase fine-dispersed Mg-B-O inhomogeneities as well as inclusions of higher borides with near-MgB_{12} stoichiometry in the Mg-B-O matrix (with 15-37 nm average grain sizes). The possibility is shown to obtain the rather high T_{c} (37 K) and critical current densities in materials with MgB_{12} matrix (with 95% of shielding fraction as calculated from the resistant curve).

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Structure and Transport Characteristics of Tunnel Junctions with Hybrid Semiconductor Barriers with Quantum Dots

Nanostructural Superconducting Materials for Fault Current Limiters and Cryogenic Electrical Machines