Imaging Spatial Distribution of Photogenerated Carriers in Monolayer MoS2 with Kelvin Probe Force Microscopy

Woongbin Yim; Van Tu Nguyen; Quynh Thi Phung; Hwan Sik Kim; Yeong Hwan Ahn; Soonil Lee; Ji-Yong Park

doi:10.1021/acsami.2c06315

Imaging Spatial Distribution of Photogenerated Carriers in Monolayer MoS₂ with Kelvin Probe Force Microscopy

ACS Appl Mater Interfaces. 2022 Jun 8;14(22):26295-26302. doi: 10.1021/acsami.2c06315. Epub 2022 May 25.

Authors

Woongbin Yim¹, Van Tu Nguyen², Quynh Thi Phung¹, Hwan Sik Kim¹, Yeong Hwan Ahn¹, Soonil Lee¹, Ji-Yong Park¹

Affiliations

¹ Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea.
² Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam.

PMID: 35613454
DOI: 10.1021/acsami.2c06315

Abstract

The spatial distribution of photogenerated carriers in atomically thin MoS₂ flakes is investigated by measuring surface potential changes under light illumination using Kelvin probe force microscopy (KPFM). It is demonstrated that the vertical redistribution of photogenerated carriers, which is responsible for photocurrent generation in MoS₂ photodetectors, can be imaged as surface potential changes with KPFM. The polarity of surface potential changes points to the trapping of photogenerated holes at the interface between MoS₂ and the substrate as a major mechanism for the photoresponse in monolayer MoS₂. The temporal response of the surface potential changes is compatible with the time constant of MoS₂ photodetectors. The spatial inhomogeneity in the surface potential changes at the low light intensity that is related to the defect distribution in MoS₂ is also investigated.

Keywords: Kelvin probe force microscopy; MoS2; interface; photogating; photoresponse.