Band Alignment at Au/MoS2 Contacts: Thickness Dependence of Exfoliated Flakes

• Published in: Journal of physical chemistry. C 2017-10, Vol.121 (40), p.22517-22522
• Main Authors: Sohn, Ahrum, Moon, Hankyoul, Kim, Jayeong, Seo, Miri, Min, Kyung-Ah, Lee, Sang Wook, Yoon, Seokhyun, Hong, Suklyun, Kim, Dong-Wook
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b07511

We investigated the surface potential (V surf) of exfoliated MoS2 flakes on bare and Au-coated SiO2/Si substrates using Kelvin probe force microscopy. The V surf of MoS2 single layers was larger on the Au-coated substrates than on the bare substrates; our theoretical calculations indicate that this may be caused by the formation of a larger electric dipole at the MoS2/Au interface leading to a modified band alignment. V surf decreased as the thickness of the flakes increased until reaching the bulk value at a thickness of ∼20 nm (∼30 layers) on the bare and ∼80 nm (∼120 layers) on the Au-coated substrates, respectively. This thickness dependence of V surf was attributed to electrostatic screening in the MoS2 layers. Thus, a difference in the thickness at which the bulk V surf appeared suggests that the underlying substrate has an effect on the electric-field screening length of the MoS2 flakes. This work provides important insights to help understand and control the electrical properties of metal/MoS2 contacts.