基于磁圆二向色谱的单层MoS_2激子能量和线宽温度依赖特性  

Temperature dependent excitonic transition energies and linewidths of monolayer MoS_2 probed by magnetic circular dichroism spectroscopy

作　　者：吴元军[1,2] 申超 谭青海[1,2] 张俊 谭平恒 郑厚植[1,2] Wu Yuan-Jun;Shen Chao;Tan Qing-Hai;Zhang Jun;Tan Ping-Heng;Zheng Hou-Zhi(State Key Laboratory of Superlattices and Microstructures,Institute of Semiconductors,Chinese Academy of Sciences Beijing 100083,China;College of Materials Science and Opto-Electronic Technology,University of Chinese Academy of Sciences Beijing 101408,China)

机构地区：[1]中国科学院半导体研究所半导体超晶格国家重点实验室,北京100083 [2]中国科学院大学材料科学与光电技术学院,北京101408

出　　处：《物理学报》2018年第14期230-238,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11404324;11574305;51527901)资助的课题~~

摘　　要：以二硫化钼(MoS_2)为代表的过渡金属硫属化物属于二维层状材料,样品可以薄至单层.单层MoS_2是一种直接带隙半导体,在纳米逻辑器件、高速光电探测、纳米激光等领域具有广阔的应用前景.在实际应用中,温度是影响半导体材料能带结构和性质的主要因素之一.因此研究单层二维材料能带的温度依赖特性对理解其物理机理以及开展器件应用具有重要的意义.目前,在广泛采用的测量单层MoS_2反射谱的研究中,激子峰往往叠加在一个很强的光谱背底上,难以准确分辨激子的峰位和线宽.基于自行搭建的显微磁圆二向色谱系统,研究了单层MoS_2在65—300 K温度范围内的反射谱和磁圆二向色谱,结果表明磁圆二向色谱在研究单层材料激子能量和线宽方面具有明显的优势.通过分析变温的磁圆二向色谱,得到了不同温度下的A,B激子的跃迁能量和线宽.通过对激子能量和线宽的温度依赖关系进行拟合,进一步讨论了声子散射对激子线宽的影响.Layered transition metal dichalcogenides（TMDs）, as a new class of two-dimensional material, have received wide attention of scientific community due to their peculiar electronic and optical properties. Monolayer TMDs such as MoS2,MoSe2, WS2 and WSe2 are semiconductors with band gap energies in the visible and near-infrared region, which promises the applications in logic nano-devices, ultra-high speed photoelectric detectors and nano-lasers. Temperature has strong influences on the electronic and optical properties of semiconductors, and their applications in photonic and optoelectronic devices. Thus, the research on the temperature dependence of the energy band of monolayer TMDs is important and meaningful. Monolayer MoS2, as a prototype of TMDs, displays a weak absorption line with a strong background in original reflection or absorption spectra. The strong background has a tremendous influence on the determination of excitonic transition energy and linewidth. In this work, we adopt the reflection magnetic circular dichroism（MCD）spectroscopy in which reflection spectra and MCD spectra can be simultaneously obtained. We demonstrate that the background disturbance is eliminated in the MCD spectra, in contrast to the reflectivity spectra. And we discuss the optimization of our home-built experimental setup in detail. Through the elaborate analysis of the MCD theory, we demonstrate that the excitonic transition energy and linewidth can be directly and accurately extracted from the MCD spectrum. We perform the reflection MCD measurements on monolayer MoS2 in a temperature range of 65—300 K. The transition energies and linewidths of A and B excitons of monolayer MoS2 are extracted, respectively. Those functional parameters that describe the temperature dependence of the energy and linewidth of both excitonic transitions are evaluated and analyzed. We find that the broadening of the linewidth is related to the LO phonon scattering, and the linewidth of A exciton is clearly narrower than that of B exciton. Th

关 键 词：磁光 磁圆二向色谱 单层MoS2 过渡金属硫化物 

分 类 号：O657.7[理学—分析化学] TQ136.12[理学—化学]