藉由外加應力探討單層二硫化鉬的形變位能

Abstract

本論文利用顯微拉曼與光激螢光光譜探討單層二硫化鉬的應力可調性。首先，我們透過拉曼模態的位移與分裂來量測聲子的格林奈森參數與切形變位能。接著，我們透過對樣品施加對稱(非對稱)平面應力來量測能帶形變位能中的等向(不等向)貢獻。從k．p理論的觀點出發，我們發現等向與不等向的貢獻分別正比於外加應力的一次方與二次方。此結論與密度泛函理論的計算結果一致。我們的實驗與理論結果相當符合並顯示等向貢獻主導了能隙的變化。此外，巨大的能隙改變證明了應力工程是一個調控單層二硫化鉬特性的優良泛用方法。

The strain-tunability of monolayer molybdenum disulfide (MoS2) was investigated by micro-Raman and photoluminescence spectroscopy. First of all, the Grüneisen parameter and phonon shear deformation potential of Raman-active modes were determined by the shift and split under applied strain. Then, the isotropic (anisotropic) component of bandgap deformation potential was determined by applying symmetric (asymmetric) in-plane strain. From the view of k．p theory, the isotropic (anisotropic) term is proportional to first order(second order), which is also confirmed by the density functional theory. Our results indicate the domination of the isotropy term and show good agreements between experiment and theory. Furthermore, the large bandgap shift shows that strain engineering is an exceptional and wide strategy to control properties of monolayer MoS2.