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

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 ) 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.

Keywords:

• topological insulator
• bismuth selenide
• bismuth telluride
• plasma etching
• Raman spectroscopy
• atomic force microscopy

Acknowledgements

This work has been partially supported by the Mesodynamic Architectures program of the Defense Advanced Research Projects Agency. Yong P. Chen also acknowledges support from the Miller Family Endowment.