Magnozzi Michele, Pflug Theo, Ferrera Marzia, Pace Simona, Ramó Lorenzo, Olbrich Markus, Canepa Paolo, Ağircan Hasret, Horn Alexander, Forti Stiven, Cavalleri Ornella, Coletti Camilla, Bisio Francesco, Canepa Maurizio
OptMatLab, Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, 16146 Genova, Italy.
Istituto Nazionale di Fisica Nucleare, Sezione di Genova, via Dodecaneso 33, 16146 Genova, Italy.
J Phys Chem C Nanomater Interfaces. 2021 Jul 29;125(29):16059-16065. doi: 10.1021/acs.jpcc.1c04287. Epub 2021 Jul 14.
Excitons dominate the light absorption and re-emission spectra of monolayer transition-metal dichalcogenides (TMD). Microscopic investigations of the excitonic response in TMD almost invariably extract information from the radiative recombination step, which only constitutes one part of the picture. Here, by exploiting imaging spectroscopic ellipsometry (ISE), we investigate the spatial dependence of the dielectric function of chemical vapor deposition (CVD)-grown WS flakes with a microscopic lateral resolution, thus providing information about the spatially varying, exciton-induced light absorption in the monolayer WS. Comparing the ISE results with imaging photoluminescence spectroscopy data, the presence of several correlated features was observed, along with the unexpected existence of a few uncorrelated characteristics. The latter demonstrates that the exciton-induced absorption and emission features are not always proportional at the microscopic scale. Microstructural modulations across the flakes, having a different influence on the absorption and re-emission of light, are deemed responsible for the effect.
激子主导着单层过渡金属二硫属化物（TMD）的光吸收和再发射光谱。对TMD中激子响应的微观研究几乎总是从辐射复合步骤中提取信息，而这只是其中一部分情况。在此，通过利用成像光谱椭偏仪（ISE），我们以微观横向分辨率研究了化学气相沉积（CVD）生长的WS薄片介电函数的空间依赖性，从而提供了关于单层WS中空间变化的、激子诱导的光吸收的信息。将ISE结果与成像光致发光光谱数据进行比较，观察到了几个相关特征的存在，同时还意外地发现了一些不相关的特征。后者表明，在微观尺度上，激子诱导的吸收和发射特征并不总是成比例的。薄片上的微观结构调制对光的吸收和再发射有不同影响，被认为是造成这种效应的原因。
