Surface-bulk coupling in a Bi2Te3 nanoplate grown by van der Waals epitaxy

Xiaobo Li; Mengmeng Meng; Shaoyun Huang; Congwei Tan; Congcong Zhang; Hailin Peng; H Q Xu

doi:10.1039/d1nr08054g

Surface-bulk coupling in a Bi₂Te₃ nanoplate grown by van der Waals epitaxy

Nanoscale. 2022 Feb 17;14(7):2586-2592. doi: 10.1039/d1nr08054g.

Authors

Xiaobo Li^{1

2}, Mengmeng Meng¹, Shaoyun Huang¹, Congwei Tan³, Congcong Zhang³, Hailin Peng³, H Q Xu^{1

4}

Affiliations

¹ Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China. hqxu@pku.edu.cn.
² Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
³ Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
⁴ Beijing Academy of Quantum Information Sciences, Beijing 100193, China.

PMID: 35132985
DOI: 10.1039/d1nr08054g

Abstract

We report an experimental study of the effect of coherent surface-bulk electron scattering on quantum transport in a three-dimensional topological insulator Bi₂Te₃ nanoplate. The nanoplate is grown via van der Waals epitaxy on a mica substrate and a top-gated Hall-bar device is fabricated from the nanoplate directly on the growth substrate. Top-gate voltage dependent measurements of the sheet resistance of the device reveal that the transport carriers in the nanoplate are of n-type and that, with decreasing top gate voltage, the carrier density in the nanoplate is decreased. However, the mobility is increased with decreasing top-gate voltage. This mobility increase with decreasing carrier density in the nanoplate is demonstrated to arise from a decrease in bulk-to-surface electron scattering rate. Low-field magnetotransport measurements are performed at low temperatures. The measured magnetoconductivity of the nanoplate shows typical weak anti-localization (WAL) characteristics. We analyze the measurements by taking surface-bulk inter-channel electron scattering into account and extract dephasing times τ_φ, diffusion coefficients D of electrons at the top surface and in the bulk, and the surface-bulk scattering times τ_SB as a function of top-gate voltage and temperature. It is found that the dephasing in the nanoplate arises dominantly from electron-electron scattering with small energy transfers. It is also found that the ratio of τ_φ/τ_SB (a measure of the surface-bulk electron coherent coupling) is decreased with decreasing gate voltage or increasing temperature. We demonstrate that taking the surface-bulk coherent electron scattering in our Bi₂Te₃ nanoplate into account is essential to understand quantum transport measurements at low temperatures.