Systematic Comparison of Eight Substrates in the Growth of FeSe$_{0.5}$Te$_{0.5}$ Superconducting Thin Films

TL;DR

This study compares the growth and properties of FeSe$_{0.5}$Te$_{0.5}$ superconducting thin films on eight different substrates, revealing that in-plane orientation and lattice parameter ratio influence superconductivity more than lattice mismatch.

Contribution

It systematically analyzes how substrate choice affects the structural and superconducting properties of FeSe$_{0.5}$Te$_{0.5}$ thin films, highlighting the importance of surface layers and lattice ratios.

Findings

Superconductivity correlates with in-plane orientation and c/a ratio, not lattice mismatch.

Films on MgO and LaAlO$_3$ exhibit the highest T_c of 9.5 K.

Presence of amorphous-like layer at substrate surface affects film quality.

Abstract

We have investigated the crystal structures and superconducting properties of thin films of FeSe$_{0.5}$Te$_{0.5}$ grown on eight different substrates. Superconductivity is not correlated with the lattice mismatch; rather it is correlated with the degree of in-plane orientation and with the lattice parameter ratio $c/a$. The best superconducting properties were observed in films on MgO and LaAlO$_3$ ($T_\mathrm{c}^\mathrm{zero}$ of 9.5 K). TEM observation showed that the presence or absence of an amorphous-like layer at the substrate surface plays a key role in determining the structural and superconducting properties of the grown films.