AFM and Raman studies of topological insulator materials subject to argon plasma etching

TL;DR

This study investigates how argon plasma etching affects the physical and spectral properties of topological insulator materials, providing insights into their surface modification for nano-device fabrication.

Contribution

It offers detailed AFM and Raman analysis of plasma-induced changes in topological insulators, including etching rates and spectral peak modifications, which were previously uncharacterized.

Findings

Plasma exposure reduces sample thickness and increases surface roughness.

Raman peaks widen without shifting, and intensity varies with etching depth.

Etching rates differ among materials, informing fabrication processes.

Abstract

Plasma etching is an important tool in nano-device fabrication. We report a study on argon plasma etching of topological insulator materials Bi2Se3, Bi2Te3, Sb2Te3 and Bi2Te2Se using exfoliated flakes (with starting thicknesses of ~100 nm) derived from bulk crystals. We present data mainly from atomic force microscopy (AFM) and Raman spectroscopy. Through AFM measurements, plasma exposure is observed to decrease the thickness of our samples and increase surface roughness (with height fluctuations reaching as large as ~20 nm). We extract an etching rate for each type of material. Plasma exposure also causes a widening (especially Eg2) of the characteristic Raman peaks, with no significant change in peak position. The overall Raman intensity is observed to initially increase, then decrease sharply after the samples are etched below ~20 nm in thickness. Our findings are valuable for understanding the effects of argon plasma etching on topological insulator materials.