Chemical Vapor Deposition Growth of Three-Dimension Topological Insulator $Bi_2(Se_xTe_{1-x})_3$

Abstract

Binary topological insulator $Bi_2X_3$ ($X=Te, \ Se$) nanoplates have been synthesised via catalyst free chemical vapor deposition method. A silicon nitride protecting layer was deposited to measure the Raman spectra for those nanoplates without introducing damage to the sample surface. Temperature dependent nonresonant Raman spectra at the excitation of $512.5 \ \text{nm}$ show rather small first-order temperature coefficients for all Raman modes in $Bi_2Te_3$ and $Bi_2Se_3$ nanoplates compared to the reported value in bulk single crystal. Besides, the $A_{1g2}$ mode shows electronic resonant enhancement in the Raman spectra at the excitation of $633 \ \text{nm}$, which gives a similar small first-order temperature coefficient as the non-resonant one. Magnetotransport measurement for grown $Bi_2Se_3$ nanoplate shows pronounced weak anti-localization effect in the low field region, linear magnetoresistance in the perpendicular high field and a weak negative magnetoresistance in the in-plane direction. All the magnetotransport signatures are expected to originate from the topological surface states.