Influence of Defect Structures on Intervalley Scattering in Two-dimensional WSe_(2) Revealed by Double-Resonance Raman Spectroscopy  

双共振拉曼光谱揭示二维二硒化钨材料中缺陷结构对谷间散射的影响

作　　者：Yueqing Zhang Yao Zhang Zhen-Chao Dong 张月箐;张尧;董振超(中国科学技术大学合肥微尺度物质科学国家研究中心,中国科学院量子信息与量子科技创新研究院,合肥230026)

机构地区：[1]Hefei National Research Center for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information&Quantum Physics,University of Science and Technology of China,Hefei 230026,China

出　　处：《Chinese Journal of Chemical Physics》2025年第1期25-36,I0055,共13页化学物理学报(英文)

基　　金：supported by the National Natural Sci-ence Foundation of China(No.22174135,No.21790352);the National Key R&D Program of China(No.2021YFA1500500,No.2016YFA0200600);the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000);Anhui Initiative in Quantum Information Technologies(No.AHY090100);CAS Project for Young Scientists in Basic Research(No.YSBR-054);Innovation Program for Quantum Science and Technology(No.2021ZD0303301);the Fundamental Research Funds for the Central Universities.

摘　　要：Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.二维材料中的双共振拉曼散射描述了由入射光子激发的电子或空穴的谷内(谷间)散射。通常缺陷的存在可以提供额外的动量,并影响涉及一个或两个声子的散射过程,但传统的双共振拉曼理论仅考虑了没有任何结构细节的理想化缺陷。本文计算了具有不同类型缺陷的单层二硒化钨在布里渊区K(K')和M点附近的声学声子和光学声子不同组合的二阶双共振拉曼光谱.由于缺陷的存在会导致电子能带结构发生改变,本文采用了能带反折叠的方法来展示缺陷导致的单层二硒化钨价带和导带的弯曲.不同缺陷对应的声子能带结构也表现出不同的变化,从而导致具有不同类型缺陷的单层二硒化钨相对应的双共振拉曼光谱各不相同.例如,钨空位的存在会导致单层二硒化钨大多数合频模式的频率红移和不对称展宽,可以归因于K和K'处电子谷的轮廓发生了显著变化.此外,由于Q点处导带的升高,对于双硒空位从K到Q的双共振拉曼散射是被禁止的。总之,本工作强调了缺陷结构在谷间散射中的作用,并为更好理解二维材料双共振拉曼过程的物理机制提供了依据。

关 键 词：2D materials Tungsten diselenide Intervalley scattering Double-resonance Ra-man Defect structure Band unfolding 

分 类 号：O657.37[理学—分析化学] TQ136.13[理学—化学]