MgB2 thick film with TC = 40.2 K deposited on sapphire substrate

TL;DR

This paper reports the successful fabrication of a 1.3-micron thick MgB2 superconducting film on sapphire using HPCVD, demonstrating promising properties for future superconducting applications.

Contribution

It introduces a novel application of HPCVD to produce thick MgB2 films with high critical temperature and current density on sapphire substrates.

Findings

Critical temperature of 40.2 K with sharp transition

Critical current density of 5×10^10 A/m² in zero field

Residual resistivity ratio of about 11

Abstract

We have successfully deposited thick MgB2 film on the (0001) crystalline surface of sapphire by the method of hybrid physical-chemical vapor deposition (HPCVD). The film thickness is about 1.3 micron. It has a dense and interlaced structure. The film surface, shown by SEM, is stacked with MgB2 microcrystals. Transport measurements by the 4-probe technique have demonstrated that its critical temperature is about 40.2 K, with a sharp transition width of 0.15 K. The residual resistivity ratio (RRR) is about 11. By extrapolation, HC2(0) is determined as 13.7 T from the magneto-transport measurement. Also by hysteresis measurement and applying the Bean model, the critical current density is estimated as 5*1010 A/m2 in zero magnetic field. The present work has demonstrated that HPCVD is an effective technique to fabricate the MgB2 thick film with decent superconducting properties. Hence, it is important for the future superconducting application, in particular, as a crucial preliminary stage to fabricate superconducting tape.