Su Liqin, Zhang Yong, Yu Yifei, Cao Linyou
Electrical and Computer Engineering Department, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
Nanoscale. 2014 May 7;6(9):4920-7. doi: 10.1039/c3nr06462j.
This work reports a study on the temperature dependence of in-plane E and out-of-plane A1g Raman modes of single-layer (1L) and bi-layer (2L) MoS2 films on sapphire (epitaxial) and SiO2 (transferred) substrates as well as bulk MoS2 single crystals in a temperature range of 25-500 °C. For the films on the transferred SiO2 substrate, the in-plane E mode is only weakly affected by the substrate, whereas the out-of-plane A1g mode is strongly perturbed, showing highly nonlinear, sometimes even non-monotonic, temperature dependence on the Raman peak shift and linewidth. In contrast, for the films on the epitaxial sapphire substrate, E is affected more significantly by the substrate than A1g. This study suggests that the 2-D film-substrate coupling depends sensitively on the preparation method, and in particular on the film morphology for the transferred film. These findings are vitally important for the fundamental understanding and application of this quasi 2-D material that is expected to be supported by a substrate in most circumstances.
本文报道了一项关于在25至500°C温度范围内，蓝宝石（外延）和二氧化硅（转移）衬底上的单层（1L）和双层（2L）二硫化钼（MoS2）薄膜以及块状MoS2单晶的面内E和面外A1g拉曼模式的温度依赖性研究。对于转移到二氧化硅衬底上的薄膜，面内E模式仅受到衬底的微弱影响，而面外A1g模式则受到强烈扰动，表现出高度非线性，有时甚至是非单调的，拉曼峰位移和线宽的温度依赖性。相比之下，对于外延蓝宝石衬底上的薄膜，E模式比A1g模式受到衬底的影响更显著。该研究表明，二维薄膜与衬底的耦合敏感地依赖于制备方法，特别是对于转移薄膜而言，依赖于薄膜形态。这些发现对于在大多数情况下预期由衬底支撑的这种准二维材料的基本理解和应用至关重要。
