Gate-Tunable Transport Properties of Ultra-Thin Topological Insulator Thin Film and Electrical Detection of Spin Signal

Abstract

Three-dimensional topological insulator Bi2Se3 has natural Se vacancy and causes high intrinsic n-type carrier concentration In order to research the surface state we doped Sb into Bi2Se3 to tune down the carrier concentration We successfully grew the ultra-thin Sb-doped Bi2Se3 film on sapphire and SrTiO?3 (STO) substrate do the basic electrical properties on sapphire and gate-tunable transport properties on STO An extremely large change of the sheet resistance in ultra-thin film is observed owing to the surface gap opening The on-off ratio is about 14000% On the other hand we study the spin valve device which can electrical detect the current-induced spin polarization due to spin-momentum locking The barrier between topological insulator and ferromagnetic layer is the key point to detect the signal By selecting a great barrier condition we can observe the hysteresis-like spin signal from surface state If we can combine the spin valve device with back gate and ultra-thin topological insulator film the mechanism of spin-transistor may be realized

Date of Award	2016 Aug 24
Original language	English
Supervisor	Jung-Chun Huang (Supervisor)