不同厚度三维拓扑绝缘体Sb2Te3的圆偏振光电流光谱研究

本文研究了不同厚度三维拓扑绝缘体Sb2Te3的圆偏振光致电流光谱。研究表明，在1064纳米圆偏振激光激发下，厚度为7纳米的三维拓扑绝缘体Sb2Te3薄膜的圆偏振光致电流与厚度为30纳米的样品的符号相反。原子力显微镜的分析表明30纳米的样品比7纳米的样品具有更大表面粗糙度，这使得30纳米样品的上表面态对圆偏振光致电流的贡献减小，使其下表面态的贡献占主导。而7样品的样品是上表面态的贡献占主导，从而相比厚度为30纳米的样品出现了反号。研究表明，在960纳米激光激发下，厚度为30纳米和7纳米的样品呈现相同的符号。进一步研究表明这个信号可能与InP衬底的自旋注入有关。

Investigation of the circular photogalvanic effect spectroscopy of three-dimensional topological insulator Sb2Te3 with different thickness

In this paper, the circular photogalvanic effect (CPGE) spectroscopy of three-dimensional topological insulator Sb2Te3 with different thicknesses have been investigated. It was revealed that under the illumination of 1064 nm light, the sign of the CPGE current of the 7 nm sample showed an opposite sign with that of 30 nm sample. The analysis of the atomic force microscope (AFM) images indicated that the surface roughness of the 30 nm sample was larger than that of 7 nm sample, which would lead to less contribution of the top surface to the CPGE current and the dominated contribution of the bottom surface to the CPGE current in the 30 nm sample. However, the top surface states played the dominated contribution to the CPGE current. Therefore, their signs were opposite to each other. It was demonstrated that, under the illumination of 960 nm light, the sign of the CPGE current of the 7 and 30 nm samples was the same. Further investigation revealed that the signal around 960 nm in the CPGE spectrum may relate to the spin injection from InP substrate.