Simple Synthesis of Entropy Stabilized Oxides Single Crystal Films

ABSTRACT Entropy‐stabilized oxides (ESO) have emerged in the last decade as a new class of metastable materials with promising functional properties. Here, we report a simple method for synthesizing single‐crystalline ESO layers of the ESO (CoCuMgNiZn)O using metal–organic chemical vapor deposition (MOCVD) followed by thermal annealing. A multicationic oxide layer was first deposited on single‐crystal MgO (100) substrates, and subsequent annealing steps at 700°C and 925°C promoted elemental interdiffusion and the formation of the entropy‐stabilized phase, respectively. Grazing incidence x‐ray diffraction, scanning electron microscope/energy dispersive spectroscopy, AFM, x‐ray photoelectron spectroscopy, and atomic‐resolution STEM analyses confirmed the structural evolution, chemical homogeneity, and unraveled their atomic structure. Our results demonstrate that entropy‐stabilized single‐crystal layers can be obtained by diffusion within the substrate, offering a straightforward approach for the integration of these compounds into functional devices. Moreover, atomic‐resolution scanning transmission electron microscopy measurements showed that a transition toward an entropy‐stabilized phase with spontaneous equimolar cationic composition takes place at high temperature. This is direct evidence of entropy stabilization observed at the atomic scale.