Superconducting thin films and tunnel junctions based on aluminum

Abstract

The features of conductivity in aluminum films produced by various methods are described depending on the presence of impurities, film thickness, and deposition conditions. The results of measuring the surface properties and crystal structure of fabricated films of aluminum, aluminum oxide, and aluminum nitride by X-ray diffraction and atomic force microscopy are presented. SIS, SIN, NIN junctions based on aluminum were fabricated using both shadow evaporation and magnetron sputtering. The current-voltage characteristics were measured. The prospects for improving the characteristics of aluminum SIS junctions, SQUID amplifiers, and SINIS detectors operating at temperatures of about 100 mK are discussed. Keywords: aluminum thin films, surface roughness, atomically smooth films, tunnel junctions.

Quasiepitaxial Aluminum Film Nanostructure Optimization for Superconducting Quantum Electronic Devices

“…In our previous study of Al films and tunnel junctions [ 3 ], we studied room-temperature deposited Al/AlOx/Al SIS tunnel junctions and SINIS detectors operating at temperatures down to 100 mK. We mentioned that the practical parameters for many Josephson junction devices are much worse compared to theoretical estimations for perfect interfaces with atomically smooth surfaces.…”

“…We also studied the crystal structure, surface roughness, and grain structure of magnetron-sputtered aluminum films intended for the fabrication of NIS and SIS tunnel junctions with AlOx or AlN barriers for junctions with Nb, NbN, and Al superconducting electrodes. The morphology and properties of magnetron-sputtered Nb, NbN, and Al superconducting electrodes intended for the fabrication of advanced NIS and SIS tunnel junctions with AlOx or AlN barriers were also investigated [ 3 ].…”

“…The experimental results are presented in [3], along with roughness and resistivity measurements for magnetron sputtering films at room temperature. Usually, Al films Nanomaterials 2023, 13,2002 2 of 14 are magnetron-sputtered on Si (100) substrates covered with an insulating layer of Al 2 O 3 .…”

Microwave SINIS Detectors

“…With separate cycles (lithography of one layer and deposition of the first film, and then a similar procedure for the second), the quality of the tunnel junction will be significantly worse due to the fact that uncontrolled parasitic oxides form on the surface of the first film. To solve this problem, we developed a modified directwrite technology [33,38] (Table 3, right column). The idea is to use ion etching before the deposition of the second layer in the deposition chamber.…”

“…2022, 12, x FOR PEER REVIEW 10 of 16 junction will be significantly worse due to the fact that uncontrolled parasitic oxides form on the surface of the first film. To solve this problem, we developed a modified directwrite technology [33,38] (Table 3, right column). The idea is to use ion etching before the deposition of the second layer in the deposition chamber.…”