Sercombe D, Schwarz S, Del Pozo-Zamudio O, Liu F, Robinson B J, Chekhovich E A, Tartakovskii I I, Kolosov O, Tartakovskii A I
Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
1] Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom [2] Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany.
Sci Rep. 2013 Dec 12;3:3489. doi: 10.1038/srep03489.
Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding. Here we use micro-photoluminescence (PL) and ultrasonic force microscopy to explore the influence of the dielectric environment on optical properties of a few monolayer MoS2 films. PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely. This film-to-film variation is suppressed by additional capping of MoS2 with SiO2 and Si(x)N(y), improving mechanical coupling of MoS2 with surrounding dielectrics. We show that the observed PL non-uniformities are related to strong variation in the local electron charging of MoS2 films. In completely encapsulated films, negative charging is enhanced leading to uniform optical properties. Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.
二维（2D）化合物为新型层状器件和混合光子结构提供了独特的构建块。然而，薄膜中较大的表面积与体积比增强了表面相互作用和电荷效应的重要性，这需要新的理解。在这里，我们使用微光致发光（PL）和超声力显微镜来探索介电环境对几层单层二硫化钼（MoS2）薄膜光学性质的影响。发现沉积在二氧化硅（SiO2）衬底上的MoS2薄膜的PL光谱变化很大。通过用SiO2和Si(x)N(y)对MoS2进行额外的覆盖，这种薄膜间的变化得到了抑制，改善了MoS2与周围电介质的机械耦合。我们表明，观察到的PL不均匀性与MoS2薄膜局部电子充电的强烈变化有关。在完全封装的薄膜中，负电荷增强，导致光学性质均匀。观察到二维薄膜的光学特性对表面相互作用具有极大的敏感性，这对层状材料的光电子应用具有重要意义。
