Tuning the thickness of exfoliated quasi-two-dimensional beta-Ga2O3 flakes by plasma etching

Abstract

We demonstrated the thinning of exfoliated quasi-two-dimensional beta-Ga2O3 flakes by using a reactive ion etching technique. Mechanical exfoliation of the bulk beta-Ga2O3 by using an adhesive tape was followed by plasma etching to tune its thickness. Since beta-Ga2O3 is not a van der Waals material, it is challenging to obtain ultra-thin flakes below a thickness of 100 nm. In this study, an etch rate of approximately 16 nm/min was achieved at a power of 200W with a flow of 50 sccm of SF6, and under these conditions, thinning of beta-Ga2O3 flakes from 300 nm down to similar to 60 nm was achieved with smooth morphology. We believe that the reaction between SF6 and Ga2O3 results in oxygen and volatile oxygen fluoride compounds, and non-volatile compounds such as GaFX that can be removed by ion bombardment. The opto-electrical properties were also characterized by fabricating solar-blind photodetectors using the plasma-thinned beta-Ga2O3 flakes; these detectors showed fast response and decay with excellent responsivity and selectivity. Our results pave the way for tuning the thickness of two-dimensional materials by using this scalable, industry-compatible dry etching technique. Published by AIP Publishing.