Tuning the thickness of exfoliated quasi-two-dimensional β-Ga_2O_3 flakes by plasma etching

摘要

We demonstrated the thinning of exfoliated quasi-two-dimensional β-Ga_2O_3 flakes by using a reactive ion etching technique. Mechanical exfoliation of the bulk β-Ga_2O_3 by using an adhesive tape was followed by plasma etching to tune its thickness. Since β-Ga_2O_3 is not a van der Waals material, it is challenging to obtain ultra-thin flakes below a thickness of 100nm. In this study, an etch rate of approximately 16nm/min was achieved at a power of 200W with a flow of 50 sccm of SF_6, and under these conditions, thinning of β-Ga_2O_3 flakes from 300nm down to ～60nm was achieved with smooth morphology. We believe that the reaction between SF_6 and Ga_2O_3 results in oxygen and volatile oxygen fluoride compounds, and non-volatile compounds such as GaF_x that can be removed by ion bombardment. The opto-electrical properties were also characterized by fabricating solar-blind photodetectors using the plasma-thinned β-Ga_2O_3 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.