Van der Waals epitaxy of ferroelectric ε-gallium oxide thin film on flexible synthetic mica

Abstract

This study demonstrates the formation of the van der Waals epitaxy of the ε-gallium oxide (Ga2O3) thin film on cleaved synthetic mica via mist chemical vapor deposition. Orthorhombic ε-Ga2O3 (001) was epitaxially grown on synthetic mica (001). The analysis using transmission electron microscopy revealed an in-plane orientation of ε-Ga2O3 [010] ∣∣ synthetic mica [010]. However, the most thermodynamically stable β-Ga2O3 was grown at the film-substrate interface. The optical direct bandgap of the ε-Ga2O3 thin film grown by van der Waals epitaxy was estimated to be 5.0 eV, which was the same as for the heteroepitaxially grown ε-Ga2O3 thin film on other substrates. Besides, after ε-Ga2O3 thin film was grown on the synthetic mica substrates that are cleaved sufficiently thin, the sample could be bent or cut with scissors. These results denote that the epitaxial ε-Ga2O3 thin films grown by van der Waals epitaxy can be applied to flexible electronics.