Abstract
In this work, the mechanical exfoliation method has been utilized to fabricate Bi2Te3 ultrathin films. The thickness of the ultrathin films is revealed to be several tens of nanometers. Weak antilocalization effects and Shubnikov de Haas oscillations have been observed in the magneto-transport measurements on individual films with different thickness, and the two-dimensional surface conduction plays a dominant role. The Fermi level is found to be 81 meV above the Dirac point, and the carrier mobility can reach ~6030 cm2/(Vs) for the 10-nm film. When the film thickness decreases from 30 to 10 nm, the Fermi level will move 8 meV far from the bulk valence band. The coefficient α in the Hikami-Larkin-Nagaoka equation is shown to be ~0.5, manifesting that only the bottom surface of the Bi2Te3 ultrathin films takes part in transport conductions. These will pave the way for understanding thoroughly the surface transport properties of topological insulators.
Highlights
As a unique class of condense matter materials, topological insulators (TIs) have attracted considerable attention these years for their potential applications in spintronics and quantum computation [1, 2]
In order to roughly know about the distributions of Bi2Te3 micro-flakes on the SiO2/Si substrate, the optical microscopy and scanning electron microscopy (SEM) observations were performed
The precise information about the thickness of Bi2Te3 micro-flakes can be acquired in the atomic force microscopy (AFM) measurements
Summary
As a unique class of condense matter materials, topological insulators (TIs) have attracted considerable attention these years for their potential applications in spintronics and quantum computation [1, 2]. TIs are characterized by intrinsic insulating bulk states and metallic surface states due to strong spin-orbit coupling. The Dirac-like surface states of TIs are protected by charge symmetry and time reversal invariance, to guarantee it non-trivial. The electron spin is locked with its momentum and the backscattering induced by nonmagnetic impurities is prohibited. These special natures of TIs bring forth exotic phenomena, such as quantum spin Hall effect and Majorana fermions appearing in vortex cores between the interface of TI and superconductor [1,2,3,4]. After HgTe/CdTe quantum wells, Bi2Se3, Bi2Te3, and Sb2Te3 as the second generation of three-dimensional TIs were proved with angle-resolved photoemission
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