Synthesis and Properties of c-axis Oriented Epitaxial MgB2 Thin Films

TL;DR

This paper reports the successful growth of c-axis oriented epitaxial MgB2 thin films on Al2O3 substrates, analyzing their structure and superconducting properties, with implications for understanding and applying MgB2 superconductivity.

Contribution

It presents a novel method for synthesizing epitaxial MgB2 thin films with controlled orientation and characterizes their superconducting properties.

Findings

Critical temperature of 35 K achieved.

High critical current densities of 5x10^6 A/cm^2 at 4.2 K.

Epitaxial films show c-axis orientation with a 30-degree in-plane rotation.

Abstract

We report the growth and properties of epitaxial MgB2 thin films on (0001) Al2O3 substrates. The MgB2 thin films were prepared by depositing boron films via RF magnetron sputtering, followed by a post-deposition anneal at 850C in magnesium vapor. X-ray diffraction and cross-sectional TEM reveal that the epitaxial MgB2 films are oriented with their c-axis normal to the (0001) Al2O3 substrate and a 30 degree rotation in the ab-plane with respect to the substrate. The critical temperature was found to be 35 K and the anisotropy ratio, Hc2(parallel to the film) / Hc2(pendicular to the film), about 3 at 25K. The critical current densities at 4.2 K and 20 K (at 1 T perpendicular magnetic field) are 5x10E6 A/cm2 and 1x10E6 A/cm2, respectively. The controlled growth of epitaxial MgB2 thin films opens a new avenue in both understanding superconductivity in MgB2 and technological applications.