Morphology of Superconducting FeSe thin films deposited by co-sputtering and MBE

TL;DR

This study compares the morphology and superconducting properties of FeSe thin films grown by sputtering and MBE, highlighting the importance of surface smoothness for future applications.

Contribution

It provides a direct comparison of FeSe thin films grown by two different methods and links surface morphology to superconducting performance.

Findings

Sputtered films are smoother with fewer precipitates.

Both methods achieve superconductivity up to 8.5 K.

MBE films show microcracks and higher roughness.

Abstract

The presumably unconventional superconductor Beta-FeSe was deposited by radio frequency sputtering and molecular beam epitaxy (MBE) from two elementary sources. Superconducting thin films were grown in (001)-orientation on MgO(100) and YAlO3(010) substrates. The morphology of the samples was studied and directly related to the superconducting properties of the Beta-FeSe thin films. The MBE grown thin films show microcracks down to the substrate and a roughness of about 100~nm. In contrast, sputter deposited superconducting thin films show a smooth surface with almost no precipitates. In both cases resistive superconducting transitions with critical temperature up to 8.5 K were observed. However, the smoothness of the sputter deposited films is crucial for future surface dependent investigations.