title: Air stable p-doping of WSe2 by covalent functionalization.
abstract: Covalent functionalization of transition metal dichalcogenides (TMDCs) is investigated for air-stable chemical doping. Specifically, p-doping of WSe(2) via NOx chemisorption at 150 °C is explored, with the hole concentration tuned by reaction time. Synchrotron based soft X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) depict the formation of various WSe(2-x-y)O(x)N(y) species both on the surface and interface between layers upon chemisorption reaction. Ab initio simulations corroborate our spectroscopy results in identifying the energetically favorable complexes, and predicting WSe(2):NO at the Se vacancy sites as the predominant dopant species. A maximum hole concentration of ∼ 10(19) cm(-3) is obtained from XPS and electrical measurements, which is found to be independent of WSe(2) thickness. This degenerate doping level facilitates 5 orders of magnitude reduction in contact resistance between Pd, a common p-type contact metal, and WSe(2). More generally, the work presents a platform for manipulating the electrical properties and band structure of TMDCs using covalent functionalization.
authors.affiliation: Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States.
authors.forename: Peida
authors.initials: P
authors.lastname: Zhao
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kiriya
authors.forename: Angelica
authors.initials: A
authors.lastname: Azcatl
authors.forename: Chenxi
authors.initials: C
authors.lastname: Zhang
authors.forename: Mahmut
authors.initials: M
authors.lastname: Tosun
authors.forename: Yi-Sheng
authors.initials: YS
authors.lastname: Liu
authors.forename: Mark
authors.initials: M
authors.lastname: Hettick
authors.forename: Jeong Seuk
authors.initials: JS
authors.lastname: Kang
authors.forename: Stephen
authors.initials: S
authors.lastname: McDonnell
authors.forename: K C
authors.initials: KC
authors.lastname: Santosh
authors.forename: Jinghua
authors.initials: J
authors.lastname: Guo
authors.forename: Kyeongjae
authors.initials: K
authors.lastname: Cho
authors.forename: Robert M
authors.initials: RM
authors.lastname: Wallace
authors.forename: Ali
authors.initials: A
authors.lastname: Javey
keywords: NO2; chemisorption; covalent binding; doping; layered materials