Solving and refining novel thin film phases using Cu X-ray radiation: the epitaxy-induced CuMnAs tetragonal phase

TL;DR

This paper introduces a combined experimental and computational method using CuKα radiation for precise atomic structure determination of thin films, enabling the solving of unknown phases stabilized by substrate stress.

Contribution

The study presents a novel approach for structure solving of thin film phases using only laboratory CuKα X-ray diffraction, surpassing simple refinement and applicable to unknown phases.

Findings

Successfully determined the tetragonal phase of epitaxial CuMnAs on GaAs.

Demonstrated the method's capability with high-resolution microscopy and stoichiometry analysis.

Provided corrections for transforming measured intensities into structure factors.

Abstract

We present a combined experimental and computational method which enables the precise determination of the atomic positions in a thin film using CuK{\alpha} radiation, only. The capabilities of this technique surpass simple structure refinement and allow solving unknown phases stabilized by substrate-induced stress. We derive the appropriate corrections to transform the measured integrated intensities into structure factors. Data collection was performed entirely on routinely available laboratory diffractometers (CuK{\alpha} radiation); the subsequent analysis was carried out by single-crystal direct methods ({\delta} recycling procedure) followed by the least-squares refinement of the structural parameters of the unit cell content. We selected an epitaxial thin film of CuMnAs grown on top of a GaAs substrate, which formed a crystal structure with tetragonal symmetry, differing from the bulk material which is orthorhombic. Here we demonstrate the new tetragonal form of epitaxial CuMnAs grown on GaAs substrate and present consistent high-resolution scanning transmission electron microscopy and stoichiometry analyses.