Zhang Hui, Ma Yaoguang, Wan Yi, Rong Xin, Xie Ziang, Wang Wei, Dai Lun
1] State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871, China [2] Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871, China.
Sci Rep. 2015 Feb 13;5:8440. doi: 10.1038/srep08440.
Monolayer molybdenum disulphide (MoS2) has attracted much attention, due to its attractive properties, such as two-dimensional properties, direct bandgap, valley-selective circular dichroism, and valley Hall effect. However, some of its fundamental physical parameters, e.g. refractive index, have not been studied in detail because of measurement difficulties. In this work, we have synthesized highly crystalline monolayer MoS2 on SiO2/Si substrates via chemical vapor deposition (CVD) method and devised a method to measure their optical contrast spectra. Using these contrast spectra, we extracted the complex refractive index spectrum of monolayer MoS2 in the wavelength range of 400 nm to 750 nm. We have analyzed the pronounced difference between the obtained complex refractive index spectrum and that of bulk MoS2. The method presented here is effective for two-dimensional materials of small size. Furthermore, we have calculated the color contour plots of the contrast as a function of both SiO2 thickness and incident light wavelength for monolayer MoS2 using the obtained refractive index spectrum. These plots are useful for both fundamental study and device application.
单层二硫化钼（MoS2）因其具有二维特性、直接带隙、谷选择性圆二色性和谷霍尔效应等吸引人的特性而备受关注。然而，由于测量困难，其一些基本物理参数，例如折射率，尚未得到详细研究。在这项工作中，我们通过化学气相沉积（CVD）方法在SiO2/Si衬底上合成了高度结晶的单层MoS2，并设计了一种测量其光学对比度光谱的方法。利用这些对比度光谱，我们提取了单层MoS2在400纳米至750纳米波长范围内的复折射率光谱。我们分析了所获得的复折射率光谱与块状MoS2的复折射率光谱之间的显著差异。这里提出的方法对于小尺寸的二维材料是有效的。此外，我们利用所获得的折射率光谱计算了单层MoS2的对比度随SiO2厚度和入射光波长变化的颜色等高线图。这些图对于基础研究和器件应用都很有用。
