标题： 光学明亮双层 WSe$_2$的绝对带隙变形势的测量 显示英文标题

标题： Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe$_2$

摘要： 过渡金属二硫属化物的双层结构表现出许多令人兴奋的特性，包括长寿命的层间激子和通过应变实现的宽禁带可调性。 文献中关于双层WSe$_2$的光学电子性质变化与应变相关变形势的实验测定的研究并不多。 我们的实验研究集中在三个广泛研究的高对称点，K$_{c}$，K$_{v}$，以及 Q$_{c}$，其中下标 c（v）表示导带（价带），位于双层WSe$_2$的布里渊区中。 通过使用纳米粒子应力器产生的局部双轴应变，理论模型以及进行空间和光谱分辨的光致发光测量，我们确定了双层WSe$_2$的Q$_{c}$-K$_{v}$间接带隙的绝对形变势为-5.10 $\pm$ 0.24 eV，以及K$_{c}$-K$_{v}$直接带隙的绝对形变势为-8.50 $\pm$ 0.92 eV。 We also show that $\approx$0.9% biaxial tensile strain is required to convert an indirect bandgap bilayer WSe$_2$ into a direct bandgap semiconductor. Moreover, we also show that a relatively small amount of localized strain $\approx$0.4% is required to make a bilayer WSe$_2$ as optically bright as an unstrained monolayer WSe$_2$. The bandgap deformation potentials measured here will drive advances in flexible electronics, sensors, and optoelectronic- and quantum photonic- devices through precise strain engineering. 显示英文摘要

摘要： Bilayers of transition-metal dichalcogenides show many exciting features, including long-lived interlayer excitons and wide bandgap tunability using strain. Not many investigations on experimental determinations of deformation potentials relating changes in optoelectronic properties of bilayer WSe$_2$ with the strain are present in the literature. Our experimental study focuses on three widely investigated high-symmetry points, K$_{c}$, K$_{v}$, and Q$_{c}$, where subscript c (v) refers to the conduction (valence) band, in the Brillouin zone of bilayer WSe$_2$. Using local biaxial strains produced by nanoparticle stressors, a theoretical model, and by performing the spatially- and spectrally-resolved photoluminescence measurements, we determine absolute deformation potential of -5.10 $\pm$ 0.24 eV for Q$_{c}$-K$_{v}$ indirect bandgap and -8.50 $\pm$ 0.92 eV for K$_{c}$-K$_{v}$ direct bandgap of bilayer WSe$_2$. We also show that $\approx$0.9% biaxial tensile strain is required to convert an indirect bandgap bilayer WSe$_2$ into a direct bandgap semiconductor. Moreover, we also show that a relatively small amount of localized strain $\approx$0.4% is required to make a bilayer WSe$_2$ as optically bright as an unstrained monolayer WSe$_2$. The bandgap deformation potentials measured here will drive advances in flexible electronics, sensors, and optoelectronic- and quantum photonic- devices through precise strain engineering.