Plasma Etching Effects on the Transport in Topological Insulator Bi$_2$Te$_3$ Nanoplates*

Carrier transport in various topological insulators (TIs) such as Bi$_2$Se$_3$ and Bi$_2$Te$_3$ exhibits a novel linear magneto-resistance (LMR) [1] in addition to the more extensively studied weak anti-localization effect. The robustness against raising temperature and 2D nature of this LMR [1] allude to its connection with the topologically protected 2D surface transport in TI. In this work, we study how the plasma etching induced surface roughness or corrugation impacts the transport in TI Bi$_2$Te$_3$ nanoplates, to understand how the topological surface transport responds to controlled perturbation to material surface. Bi$_2$Te$_3$ nanoplates with varied thickness were grown using CVD method and hall bar devices were studied under different Argon plasma etching conditions. Our experiments show that plasma etching induces drastic change in the Hall coefficient but has relatively weak effect on the LMR. We will also discuss the data analyzed by the two band carrier m! a ngo-transport model which allows quantitative separation of the surface carrier concentration and mobility from the bulk carriers.