Optimization of fabrication processes for Nb, NbN, NbTiN films and high-quality tunnel junctions for terahertz receiving circuits.

Abstract

This paper describes the optimization of the existing technology for the fabrication of superconducting films and high-quality tunnel junctions on a magnetron sputtering facility. To expand the frequency range to 1.1 THz and to obtain the limiting parameters of superconducting elements, the regimes of production of Nb, NbN, NbTiN films were optimized. These films are used to fabricate superconductor-insulator-superconductor Nb/Al--AlN/NbN tunnel junctions. Al and NbTiN films are required to create receiving elements at frequencies above 700 GHz (the cutoff frequency for niobium); such structures are being developed for the radio astronomy array receiver located in the Atacama Pathfinder Experiment telescope. Keywords: superconductivity, tunnel junctions, magnetron sputtering, thin films.

Fabrication of High-Quality Josephson Junctions Based on Nb|Al-AlN|NbN

“…Its sputtering is performed with the help of DC magnetron with Nb target in the atmosphere of Ar:N 2 10:1 gas mixture. The film production modes and their calibration are described in more detail in the work [6,7].…”

Experimental method for controlling the overheating of superconducting films under the action of a pulsed current

“…NbN films have a high specific resistance in the normal state and are at present used in many applied and fundamental researches. Ultrathin NbN films and fibers are used in producing logical devices [1], bolometers [2], resonators [3], terahertz radiation receivers [4], voltage standards [5] and other devices widely used in measurement instrumentation. Wide and relatively thick (units of micrometers) niobium nitride films are used in energy storage devices [6].…”