Interface control by homoepitaxial growth in pulsed laser deposited iron chalcogenide thin films.

Sebastian Molatta,Sabine Wurmehl,Ruben Hühne,Silvia Haindl,Sascha Trommler,Michael Schulze

doi:10.1038/srep16334

Abstract

Thin film growth of iron chalcogenides by pulsed laser deposition (PLD) is still a delicate issue in terms of simultaneous control of stoichiometry, texture, substrate/film interface properties, and superconducting properties. The high volatility of the constituents sharply limits optimal deposition temperatures to a narrow window and mainly challenges reproducibility for vacuum based methods. In this work we demonstrate the beneficial introduction of a semiconducting FeSe1−xTex seed layer for subsequent homoepitaxial growth of superconducting FeSe1−xTex thin film on MgO substrates. MgO is one of the most favorable substrates used in superconducting thin film applications, but the controlled growth of iron chalcogenide thin films on MgO has not yet been optimized and is the least understood. The large mismatch between the lattice constants of MgO and FeSe1−xTex of about 11% results in thin films with a mixed texture, that prevents further accurate investigations of a correlation between structural and electrical properties of FeSe1−xTex. Here we present an effective way to significantly improve epitaxial growth of superconducting FeSe1−xTex thin films with reproducible high critical temperatures (≥17 K) at reduced deposition temperatures (200 °C–320 °C) on MgO using PLD. This offers a broad scope of various applications.

Highlights

IntroductionThersleff suggested the implementation of an iron buffer layer might work for other Fe based superconductors which was shown by Iida et al
MgO (202) reflection. (b) For various films grown at the same temperature, TD = 300 °C
A beneficial diffusion barrier was introduced by Ichinose et al.22 for the FeSe1−xTex thin film growth on CaF2 substrates

Summary

Introduction

Thersleff suggested the implementation of an iron buffer layer might work for other Fe based superconductors which was shown by Iida et al.. A beneficial diffusion barrier was introduced by Ichinose et al. for the FeSe1−xTex thin film growth on CaF2 substrates. In the case of the deposition on MgO substrates, the seed layer is clearly not a diffusion barrier, but decreases the lattice constant mismatch, enables deposition at lower temperatures and, results in better controllable growth of superconducting FeSe1−xTex thin films. Unlike the iron buffer layer, the FeSe1−xTex seed layer shows no metallic, but semiconducting behavior at low temperatures without detrimental ferromagnetism. It may be advantageous for conductor fabrication on IBAD-MgO or other applications

Methods

Results

Conclusion