Physics Department, Temple University, Philadelphia PA 19122, USA.
Department of Physics, Tampere University of Technology, Tampere, Finland.
Sci Rep. 2017 Jan 13;7:40559. doi: 10.1038/srep40559.
Recent progress in the synthesis of monolayer MoS, a two-dimensional direct band-gap semiconductor, is paving new pathways toward atomically thin electronics. Despite the large amount of literature, fundamental gaps remain in understanding electronic properties at the nanoscale. Here, we report a study of highly crystalline islands of MoS grown via a refined chemical vapor deposition synthesis technique. Using high resolution scanning tunneling microscopy and spectroscopy (STM/STS), photoemission electron microscopy/spectroscopy (PEEM) and μ-ARPES we investigate the electronic properties of MoS as a function of the number of layers at the nanoscale and show in-depth how the band gap is affected by a shift of the valence band edge as a function of the layer number. Green's function based electronic structure calculations were carried out in order to shed light on the mechanism underlying the observed bandgap reduction with increasing thickness, and the role of the interfacial Sulphur atoms is clarified. Our study, which gives new insight into the variation of electronic properties of MoS films with thickness bears directly on junction properties of MoS, and thus impacts electronics application of MoS.
最近在合成单层 MoS 方面的进展为原子薄电子学铺平了新的道路，MoS 是一种二维直接带隙半导体。尽管有大量的文献，但在理解纳米尺度的电子特性方面仍然存在基本差距。在这里，我们报告了一种通过改进的化学气相沉积合成技术生长的高结晶 MoS 岛的研究。使用高分辨率扫描隧道显微镜和光谱（STM/STS）、光电子发射电子显微镜/光谱（PEEM）和 μ-ARPES，我们研究了 MoS 的电子特性作为纳米尺度上层数的函数，并深入展示了能带隙如何受到价带边缘随层数变化的影响。为了阐明观察到的带隙随厚度增加而减小的机制，进行了基于格林函数的电子结构计算，并阐明了界面硫原子的作用。我们的研究深入了解了 MoS 薄膜电子特性随厚度的变化，这直接影响 MoS 的结特性，从而影响 MoS 的电子应用。
