Raman spectroscopy of Bi2Se3-xTex (x = 0–3) topological insulator crystals

We report crystal growth and Raman spectroscopy characterization of pure and mixed bulk topological insulators Bi₂Se_3-xTe_x (x = 0–3). The series comprises of both binary (Bi₂Se₃, Bi₂Te₃) and ternary tetradymite (Bi₂Se₁Te₂, Bi₂Se₂Te₁, Bi₂Se_1·5Te_1.5) topological insulators. We analyzed in detail the Raman peaks of vibrational modes viz. out of plane A₁¹g, A₁²g and in-plane E_g² for both binary and ternary tetradymite topological insulators. Both out of plane A₁¹g and A₁²g exhibit obvious atomic size dependent peak shift and the effect is much lesser for the former than the later. The situation is rather interesting for in-plane E_g², which not only show the shift but rather a broader hump like structure. The de-convolution of the same show two clear peaks, which are understood in terms of the presence of separate in plane Bi–Se(I) and Bi–Te(I) modes in mixed tetradymite (Bi₂Se₂Te₁ and Bi₂Se_1·5Te_1.5) topological insulators. Summarily, various Raman modes of well-characterized pure and mixed topological insulator single crystals are reported and discussed in this article.