Thickness dependence of the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition

TL;DR

This study investigates how the thickness of epitaxial MgB2 thin films influences their superconducting and normal-state properties, revealing optimal thickness conditions for superior performance.

Contribution

It demonstrates that film thickness, rather than deposition rate, primarily determines MgB2 film properties, achieving record-high superconducting quality.

Findings

Increased film thickness improves Tc and reduces resistivity.

Optimal properties are achieved at thicknesses above 300 nm.

Record superconducting properties are reported for MgB2 films.

Abstract

We have studied the effect of deposition rate and layer thickness on the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition on 4H-SiC substrates. The MgB2 film deposition rate depends linearly on the concentration of B2H6 in the inlet gas mixture. We found that the superconducting and normal-state properties of the MgB2 films are determined by the film thickness, not by the deposition rate. When the film thickness was increased, the transition temperature, Tc, increased and the residual resistivity, rho0, decreased. Above about 300 nm, a Tc of 41.8 K, a rho0 of 0.28 mikroOhm.cm, and a residual resistance ratio RRR of over 30 were obtained. These values represent the best MgB2 properties reported thus far.