Surface dominated transport in single crystalline nanoflake devices of topological insulator Bi1.5Sb0.5Te1.8Se1.2

TL;DR

This study demonstrates surface-dominated electronic transport in single crystalline nanoflake devices of the topological insulator Bi1.5Sb0.5Te1.8Se1.2, highlighting potential for advanced spintronic applications.

Contribution

It provides experimental evidence of surface transport dominance in nanoflake devices and quantifies the surface contribution using resistivity, Hall analysis, and magneto-resistance measurements.

Findings

~99% surface transport in 200 nm thick nanoflakes

Observation of ambipolar electric field effect

Confirmation of surface transport via phase coherence length

Abstract

We report experimental evidence of surface dominated transport in single crystalline nanoflake devices of topological insulator Bi1.5Sb0.5Te1.8Se1.2. The resistivity measurements show dramatic difference between the nanoflake devices and bulk single crystal. The resistivity and Hall analysis based on a two-channel model indicates that ~99% surface transport contribution can be realized in 200 nm thick BSTS nanoflake devices. Using standard bottom gate with SiO2 as a dielectric layer, pronounced ambipolar electric field effect was observed in devices fabricated with flakes of 100 - 200 nm thick. Moreover, angle-dependent magneto-resistances of a nanoflake device with thickness of 596 nm are fitted to a universal curve for the perpendicular component of the applied magnetic field. The value of phase coherence length obtained from 2D weak antilocalization fitting further confirmed the surface dominated transport. Our results open a path for realization of novel electric and spintronic devices based on the topological helical surface states.