Gate-tunable coherent transport in Se-capped Bi2Se3 grown on amorphous SiO2/Si

Abstract

A topological insulator (TI) is an exotic material that has a bulk insulating gap and metallic surface states with unique spin-momentum locking characteristics. Despite its various important applications, large scale integration of TI into MOSFET technologies and its coherent transport study are still rarely explored. Here, we report the growth of high quality Bi2Se3 thin film on amorphous SiO2/Si substrate using MBE. By controlling the thickness of the film at ∼7 nm and capping the as grown film in situ with a 2 nm-thick Se layer, largest electrostatic field effect is obtained and the resistance is changed by almost 300%. More importantly, pronounced gate-tunable weak antilocalization (WAL) is observed, which refers to modulation of α from ∼−0.55 to ∼−0.2 by applying a back gate voltage. The analysis herein suggests that the significant gate-tunable WAL is attributable to the transition from weak disorder into intermediate disorder regime when the Fermi level is shifted downward by increasing the negative back gate voltage. Our findings may pave the ways towards the development of TI-based MOSFET and are promising for the applications of electric-field controlled spintronic and magnetic device.

Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

“…By using a selenium capping layer to protect the film, a sheet density of ∼1.5 ± 0.04 × 10 13 /cm 2 at low temperatures was reported, implying the Fermi level is close to the edge of the conduction band. More importantly, a carrier concentration as low as ∼3.5 × 10 12 /cm 2 was achieved by applying a gate voltage of −170 V. A large enhancement of the peak resistance and the saturation of the sheet density suggest that this gate voltage fully depleted the bulk carriers and transport properties are now dominated by the topological surface states [74]. Controllable switching between dominating bulk or surface states is an important step toward real device applications.…”

“…Finally, dielectric SiO 2 /Si substrates have been widely used to back gate Bi 2 Se 3 flakes [90][91][92], prompting many attempts to directly grow on these substrates [73,74,93]. Although the amorphous nature of SiO 2 /Si would hinder traditional MBE growth, Bi 2 Se 3 can still be grown by taking advantage of van der Waals epitaxy.…”

Size effect in the electronic transport of thin films of Bi2Se3

“…Thin films of Bi2Se3 were grown by the molecular beam epitaxy method on Al2O3 substrates [4,5] with thickness from 20 to 75 nm. The XRD data and the atomic content of elements analysis showed the synthesized films have Bi2Se3 composition (see Refs.…”

“…The XRD data and the atomic content of elements analysis showed the synthesized films have Bi2Se3 composition (see Refs. [4,5]). The atomic content of elements was measured by a scanning electron microscope equipped with an EDAX X-ray microanalysis attachment.…”

“…It is known that Bi2Se3 compound is the TI [4,5] with a metallic conductivity near surface and the gapless semiconductive one [6] in its bulk. Since the electroconductivity value in a bulk and near surface of such materials can differ substantially, it is of interest to "divide" them experimentally.…”