Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering
Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering
复制标题
通过应变工程对二维 InSe 薄片的直接带隙进行超灵敏可调
DOI：
10.1088/2053-1583/aaa6eb
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发表时间：
2018-04-01
期刊：
影响因子：
5.5
通讯作者：
Shi, Su-Fei
中科院分区：
文献类型：
--
作者：
Li, Yang;Wang, Tianmeng;Shi, Su-Fei
InSe是层状材料家族的一员，是一种上级电子和光学材料，其从体材料到原子级薄的几层都保持直接带隙特征，并且在单层极限下保持高电子迁移率。我们，第一次，利用应变大幅修改二维（2D）InSe纳米片的带隙。我们证明，我们可以通过施加面内单轴拉伸应变到1.06%，将几层InSe薄片的带隙降低160 meV，通过施加面内单轴压缩应变到0.62%，将带隙增加79 meV，如通过光致发光（PL）光谱所证明的。约239 meV的大的可逆带隙变化产生于响应于应变的少层InSe的大的带隙变化率（带隙应变系数），约154 meV/%用于单轴拉伸应变和约140 meV/%用于单轴压缩应变，代表在2D材料中实验报道的最显著的单轴应变诱导的带隙应变系数。通过第一性原理DFT和GW计算，我们对应变引起的带隙变化有了理论上的理解。我们还证实了带隙的变化，光电导测量使用不同的光子能量的激发光。InSe在红外区域中的高度可调带隙应该能够实现广泛的应用，包括机电、压电和光电器件。
InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.