Tailoring Kinetics on a Topological Insulator Surface by Defect-Induced Strain: Pb Mobility on Bi2Te3

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• 作者：Wen-Kai Huang ; Kai-Wen Zhang ; Chao-Long Yang ; Haifeng Ding ; Xiangang Wan ; Shao-Chun Li ; James W. Evans ; Yong Han
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：July 13, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：4454-4461
• 全文大小：559K
• 年卷期：0
• ISSN：1530-6992

文摘

Heteroepitaxial structures based on Bi₂Te₃-type topological insulators (TIs) exhibit exotic quantum phenomena. For optimal characterization of these phenomena, it is desirable to control the interface structure during film growth on such TIs. In this process, adatom mobility is a key factor. We demonstrate that Pb mobility on the Bi₂Te₃(111) surface can be modified by the engineering local strain, ε, which is induced around the point-like defects intrinsically forming in the Bi₂Te₃(111) thin film grown on a Si(111)-7 × 7 substrate. Scanning tunneling microscopy observations of Pb adatom and cluster distributions and first-principles density functional theory (DFT) analyses of the adsorption energy and diffusion barrier E_d of Pb adatom on Bi₂Te₃(111) surface show a significant influence of ε. Surprisingly, E_d reveals a cusp-like dependence on ε due to a bifurcation in the position of the stable adsorption site at the critical tensile strain ε_c ≈ 0.8%. This constitutes a very different strain-dependence of diffusivity from all previous studies focusing on conventional metal or semiconductor surfaces. Kinetic Monte Carlo simulations of Pb deposition, diffusion, and irreversible aggregation incorporating the DFT results reveal adatom and cluster distributions compatible with our experimental observations.