Unveiling defect-mediated carrier dynamics in monolayer semiconductors by spatiotemporal microwave imaging

• DOI: 10.1073/pnas.2004106117
• Publication Date: 2020-06-09T00:35:06Z
• Authors: Zhaodong Chu; Chun-Yuan Wang; Jiamin Quan; Chenhui Zhang; Chao Lei; Ali Han; Xuejian Ma; Hao-Ling Tang; Dishan Abeysinghe; Matthew Staab; Xixiang Zhang; Allan H. MacDonald; Vincent Tung; Xiaoqin Li; Chih-Kang Shih; Keji Lai
• Keywords: Condensed Matter - Materials Science; Condensed Matter - Mesoscale and Nanoscale Physics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 01 natural sciences; 0104 chemical sciences

Significance

Defects in two-dimensional (2D) transition-metal dichalcogenides play a crucial role in controlling the spatiotemporal dynamics of photogenerated charge carriers, which remain poorly understood to date. In this paper, the defect-mediated carrier diffusion and recombination in WS 2 monolayers are quantitatively investigated by laser-illuminated microwave impedance microscopy. Surprisingly, the photoresponse is in general stronger in the more disordered regions and samples. Such counterintuitive observations are reconciled by spatiotemporally resolved experiments, which indicate that the electron lifetime is prolonged due to the slow release of holes from the trap states. The results reveal the intrinsic time and length scales of photocarriers in van der Waals materials, providing the guidance for implementing nanooptoelectronic devices based on 2D semiconductors.