Conversion of 2-dimensional GaSe to 2-dimensional β-Ga2O3 by thermal oxidation

We demonstrate the conversion to quasi two-dimensional (2D) beta-Ga2O3 by thermally oxidizing layered GaSe of different thicknesses (from bilayer to 100 nm). GaSe flakes were prepared by mechanical exfoliation onto Si with a 300 nm SiO2 layer, highly oriented pyrolytic graphite, and mica substrates. The flakes were then annealed in ambient atmosphere at different temperatures ranging from 600 degrees C to 1000 degrees C for 30 min. Raman spectroscopy confirmed the formation of beta-Ga2O3 in the annealed samples by comparison with the Raman spectrum of a beta-Ga2O3 reference crystal. Atomic force microscopy was employed to study the morphology and the thickness of the beta-Ga2O3 flakes. In addition, we used energy dispersive x-ray spectroscopy together with scanning electron microscopy to investigate the evolution of the composition, especially Se residuals, and the sample topography with annealing temperature. beta-Ga2O3 appears at temperatures above 600 degrees C and Se is completely evaporated at temperatures higher than 700 degrees C. The thicknesses of the resulting beta-Ga2O3 flakes are half of that of the initial GaSe flake. Here we therefore present a straightforward way to prepare 2D beta-Ga2O3 by annealing 2D GaSe.

Automated summary

In this study, we demonstrate the conversion of GaSe to quasi two-dimensional (2D) beta-Ga2O3 through thermal annealing. Characterization of the annealed samples using Raman spectroscopy and atomic force microscopy revealed the formation of beta-Ga2O3 at temperatures above 600 degrees C, with complete evaporation of Se at temperatures higher than 700 degrees C. The resulting beta-Ga2O3 flakes have half the thickness of the initial GaSe flakes.