  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.
