Air Stable p‑Doping of WSe2 by Covalent Functionalization

作者：Peida Zhao, Daisuke Kiriya, Angelica Azcatl, Chenxi Zhang, Mahmut Tosun, Yi‐Sheng Liu, Mark Hettick, Jeong Seuk Kang, Stephen John McDonnell, Santosh KC, Jinghua Guo, Kyeongjae Cho, Robert M. Wallace, Ali Javey · 发表于：ACS Nano · 年份：2014 · DOI：10.1021/nn5047844 · 被引用次数：259 · 研究领域：2D Materials and Applications、Molecular Junctions and Nanostructures、MXene and MAX Phase Materials

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.