等离子体轰击单层WS_(2)引入缺陷态对束缚激子光学性质的影响  

SPECIAL TOPIC-Modification of material properties by defects and dopants Influence of defects induced by plasma-bombarded monolayer WS_(2)on optical properties of bound excitons

作　　者：刘海洋 范晓跃 范豪杰 李阳阳 唐天鸿 王刚 Liu Hai-Yang;Fan Xiao-Yue;Fan Hao-Jie;Li Yang-Yang;Tang Tian-Hong;Wang Gang(Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(Ministry of Education),Center for Quantum Physics,School of Physics,Beijing Institute of Technology,Beijing 100081,China)

机构地区：[1]北京理工大学物理学院,量子物理实验中心,先进光电量子结构设计与测量教育部重点实验室,北京100081

出　　处：《物理学报》2024年第13期9-19,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12074033);北京理工大学科技创新计划培育专项(批准号:2022CX01007)资助的课题。

摘　　要：单层过渡金属硫化物具有原子级厚度、直接带隙、强自旋轨道耦合等优异性能,使其在自旋电子学、光电子学等领域具有重要的研究价值和广泛的应用前景.通常材料中包含多种结构缺陷,这可能是在样品制备和生长过程中形成的,也可以经过后期处理产生,这些缺陷会显著改变其物理化学性质.因此,控制和理解缺陷是调控材料性质的重要途径.本文利用氩等离子体对机械剥离的单层WS_(2)进行轰击处理,通过控制轰击时间引入不同密度的缺陷.光致发光和拉曼测试结果表明,在未改变晶格结构的前提下,引入了两种缺陷态的束缚激子,两种激子的动力学过程与中性激子相比明显变慢.对比真空和大气环境下的光致发光光谱(photoluminescence spectroscopy,PL),两种激子的强度变化呈现相反的行为.本文的研究结果可为二维材料缺陷的引入和调控以及特征光谱的研究提供依据.Monolayer transition metal dichalcogenides(TMDCs)exhibit exceptional properties including atomic-scale thickness,direct bandgap,and strong spin-orbit coupling,which make them have great potential applications in spintronics,optoelectronics,and other fields.Usually,materials contain various structural defects,which are either formed during preparation and growth or induced by subsequent treatments.These defects can significantly change their physicochemical properties.Consequently,controlling and comprehending defects is an important approach to adjusting the properties of these materials.Herein,we use Ar+plasma to bombard monolayer WS_(2),which is exfoliated mechanically,thereby introducing defects whose density is controlled by changing the bombardment duration.The photoluminescence(PL)and Raman spectroscopic measurements at different temperatures and power values are utilized to investigate the optical properties of the defects.Furthermore,time-resolved photoluminescence is employed to unveil the dynamic behaviors of free and trapped excitons.The bombardment can introduce different types of defects into typical two-dimensional(2D)TMDCs such as MoS_(2)and WS_(2).Single sulfur vacancies are frequently generated,while other defects like double sulfur vacancies or metal atom vacancies can also occur.Exciton effects dominate the optical properties of monolayer TMDCs due to reduced screening and large effective mass.At low temperatures,bound exciton emissions arise from trapped states.Our measurements reveal two types of defect-bound excitons from the PL spectra at around 1.85 eV(XB1)and 1.55 eV(XB2).Meanwhile,the Raman peaks of the samples before and after treatment exhibit no obvious changes,indicating that the lattice structure remaines unchanged.After the Ar+bombardment,the intensity of the free neutral exciton significantly decreases to 1/6 of untreated WS_(2),owing to the free exciton population and the increased non-radiative centers.The dynamic processes of these two bound excitons are considerably slower tha

关 键 词：二维半导体 WS_(2) 缺陷态 激子 

分 类 号：O469[理学—凝聚态物理]