7月14日 美国德州大学奥斯汀分校林俊孚教授学术报告：Tuning 2D Material Properties by Compressive Strain

报告人：林俊孚 （海外高层次人才计划，德州奥斯汀，上海高压科学中心）

报告题目：Tuning 2D Material Properties by Compressive Strain

时间：7月14日（周五）下午3:00

地点：唐楼A213

 

 

报告摘要如下：

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Tuning 2D Material Properties by Compressive Strain 

Jung-Fu “Afu“ Lin (林俊孚)^1,2
1. Department of Geological Sciences & Texas Materials Institute, University of Texas at Austin
2. Center for High Pressure Science and Technology Advanced Research (HPSTAR)
afu@jsg.utexas.edu
The unique properties of atomically thin layers of van der Waals (vdW) bonded crystalline solids by mechanical exfoliation or chemical synthesis have attracted significant research interests in recent years. Two key properties of these 2D materials are of particular interest to their electronic and optical functionalities: tunable band gap and charge carrier mobility/concentration. The advent of stacking (hybridizing) these 2D materials drastically further expands their functionalities into three-dimensional potentially with multiple-desired functions. Although graphene remains the focus of the 2D materials research, many other 2D and stacked 2D materials (heterostructures) have emerged including TMDs, phosphorene, silicone, among many others that remain to be explored on the periodic table. In this presentation, I will discuss strain-tuned electronic, transport, and structural properties of monolayer, multilayer, and/or stacked 2D materials including graphene, TMDs, graphene-TMD, and phosphorene at high pressures using diamond anvil cells coupled with advanced laser and synchrotron X-ray spectroscopic measurements as well as first-principles calculations [1-7].
The advent of high-pressure diamond anvil cell coupled laser/synchrotron spectroscopies has allowed in situ probes of structural, electronic, optical, and transport properties of a myriad of materials in extremes with internal energy change as high as a few eV. At applied pressures, TMDs transition from a semiconducting to a metallic state that arises from interlayer chalcogenide-chalcogenide interactions as the interlayer spacing reduces. Applied pressure also provides a clean means to tune the band gap and carrier mobility of the TMDs. The critical pressure for metallization is found to scale proportionally with film thickness in the few layer limit such that the mono-layered TMDs would undergo the metallization transition at a much higher compressive strain. On the other hand, monolayer TMDs such as 2H-MoS₂experiences the direct-indirect bandgap transition and bandgap opening at applied pressures. At high compressive strain, graphene and TMDs-graphene heterostructures show significant changes in bonding characters (sp²-sp³) and interlayer charge transfers. The emerging picture shows that 2D materials under extremes can display distinct physical characters from their ambient counterparts. I will also discuss multidisciplinary research opportunities and forefront high-pressure techniques in exploring these 2D-3D materials in extremes collaboratively [1-7].
[1] J.-S. Kim et al., J. F. Lin, Towards Band Structure and Band Offset Engineering of Monolayer Transition Metal Disulfides via Strain and Composition, submitted to 2D Materials, 2017. [2] P. Lu et al., Origin of superconductivity in the Weyl semimetal WTe2 under pressure, Phys. Rev. B, 2016. [3] T. Pandey et al., Pressure-Induced Charge Transfer Doping of Monolayer Graphene/MoS₂ Heterostructure, Small, 2016. [4] J. S. Kim et al., High pressure phonon and Raman scattering study of Mo_0.5W_0.5S₂ ternary compound, 2D Materials, 2016. [5] A. P. Nayak et al., Pressure-modulated conductivity, carrier density, and mobility of multilayered tungsten disulfide, ACS Nano, 2015. [6] A. P. Nayak et al., Pressure-dependent optical and vibrational properties of the monolayer molybdenum disulfide, Nano Lett., 2015. [7] A. P. Nayak et al., Pressure-Induced Electronic Transition in Multilayered MoS₂, Nature Communications, 2014.