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

This study demonstrates the formation of the van der Waals epitaxy of the epsilon-gallium oxide (Ga2O3) thin film on cleaved synthetic mica via mist chemical vapor deposition. Orthorhombic epsilon-Ga2O3 (001) was epitaxially grown on synthetic mica (001). The analysis using transmission electron microscopy revealed an in-plane orientation of epsilon-Ga2O3 [010] parallel to synthetic mica [010]. However, the most thermodynamically stable beta-Ga2O3 was grown at the film-substrate interface. The optical direct bandgap of the epsilon-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 epsilon-Ga2O3 thin film on other substrates. Besides, after epsilon-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 epsilon-Ga2O3 thin films grown by van der Waals epitaxy can be applied to flexible electronics. (C) 2020 The Japan Society of Applied Physics