title: Large-area synthesis of monolayer WS₂ and its ambient-sensitive photo-detecting performance.
abstract: We demonstrate the synthesis of large-area monolayer WS2 films by chemical vapor deposition (CVD) and investigate their photoresponse properties by fabricating n-type field effect transistors (FETs) with Al as the ohmic contact. Our CVD-grown monolayer WS2 shows an electron mobility of 0.91 cm(2) V(-1) s(-1) and an ON/OFF ratio of 10(6), indicating its comparable electronic properties to the mechanically exfoliated flake sample. In a vacuum, by applying a gate bias (60 V), the responsivity of the monolayer WS2 phototransistor can increase up to 22.1 A W(-1) and a decent sub-second level response time can be maintained. In contrast, in air, it shows a very fast response time of less than 4.5 ms, but at the cost of responsivity reduction to 0.24 mA W(-1). Such a distinctive ambient-sensitive photo-detecting performance can be well-explained by the pronounced effect of charge-acceptor-like O2/H2O molecule adsorption/desorption on the photocarrier transport. Our CVD-grown high quality monolayer WS2 may pave the way for developing industrial-scale optoelectronic devices for photo-detecting and chemical sensing applications. [Corrected]
authors.affiliation: State Key Laboratory of Electronic Thin Film and Integrated Device, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu, 610054, China. lichun@uestc.edu.cn.
authors.forename: Changyong
authors.initials: C
authors.lastname: Lan
authors.forename: Chun
authors.initials: C
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Yin
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu