不同转角石墨烯/MoS_(2)异质结电子结构与光学性质的第一性原理研究  

First Principles Study on the Electronic Structure and Optical Properties of Graphene/MoS_(2)Heterojunctions with Different Rotation Angles

作　　者：周潇 宋述鹏[1,2] 刘慧琪 卢泽 ZHOU Xiao;SONG Shupeng;LIU Huiqi;LU Ze(State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China;Faculty of Materials,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China)

机构地区：[1]武汉科技大学省部共建耐火材料与冶金国家重点实验室,湖北武汉430081 [2]武汉科技大学材料学部,湖北武汉430081

出　　处：《高压物理学报》2024年第5期104-113,共10页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(50901053,51771139)。

摘　　要：基于密度泛函理论的第一性原理计算方法,研究了不同扭转角下石墨烯/MoS_(2)异质结构的电子结构和光学特性。结果表明,转角后的石墨烯/MoS_(2)异质结构仍具备作为单层材料时的部分特征。在费米能级附近,石墨烯层保持了其特殊的线性色散能带结构,狄拉克锥上的直接带隙Eg受到层间旋转调制的影响。异质结构中的MoS_(2)层对层厚具有高度的敏感性,随着厚度的增加,其间接带隙持续增大。当转角为10.9°时,Eg的最大值为11.67 meV。差分电荷密度计算结果表明,随着旋转角度的改变,MoS_(2)层中Mo-S间的电子转移引起了Mo-S键长的变化,从而增大了S-S层间距。同时,通过与MoS_(2)结合形成异质结构,石墨烯获得了较高的载流子浓度,异质结界面间旋转使空穴掺杂载流子浓度提高至9.2×10^(12)cm^(-2),比未转角时提高约6倍。异质结构的光学性质计算结果表明:当转角为27.0°时,其吸收边发生红移,并向低能区移动了0.233 eV;当转角为10.9°时,其吸收边发生蓝移,并向高能区移动0.116 eV,同时,在可见光范围内,异质结构损失函数下降了0.007。研究结果可为设计新型具有转角特征石墨烯异质结构的光学纳米器件提供理论参考。Based on the density functional theory(DFT),first-principles calculations were performed to investigate the electronic structures and optical properties of graphene/MoS_(2)heterostructures at several different twist angles.The results indicate that the twisted graphene/MoS_(2)heterostructures still preserve some characteristics inherent in monolayer structure.Near the Fermi level,the characteristic linear dispersion band structure of graphene layer is retained,and the direct bandgap(Eg)at the Dirac cone is influenced by interlayer rotation modulation.The bandgap of MoS_(2)layer exhibits a high sensitivity to layer thickness that the indirect bandgap continuously increases with the increase thickness.At a twist angle of 10.9°,the maximum value of Eg reaches 11.67 meV.The calculated differential charge density result indicates that with the interlayer rotations the Mo―S bond length is changed by the electron transfer between Mo and S atoms,resulting in a increasing of S-S interlayer distance.Simultaneously,the carrier concentration of graphene is increased when it forms a heterostructure with MoS_(2).The rotation at the heterojunction interface increases the hole-doped carrier concentration to 9.2×10^(12)cm^(−2),approximately six times higher than that without twist angle.The results of the optical property calculations for the heterostructures indicate that at a twist angle of 27.0°,its absorption edge undergoes a redshift to the lower energy by 0.233 eV.At a twist angle of 10.9°,the absorption edge undergoes a blue shift,moving towards the higher energy by 0.116 eV.Within the visible light range,the loss function of graphene/MoS_(2)heterostructure decreases by 0.007.This study can provide a theoretical basis for the design of new rotation graphene heterostructures optical nanodevices.

关 键 词：石墨烯/MoS_(2)异质结 光学性质 电子结构 扭转角 载流子浓度 

分 类 号：O469[理学—凝聚态物理] O47[理学—电子物理学]