Air Stable p‑Doping of WSe<sub>2</sub> by Covalent Functionalization Peida Zhao Daisuke Kiriya Angelica Azcatl Chenxi Zhang Mahmut Tosun Yi-Sheng Liu Mark Hettick Jeong Seuk Kang Stephen McDonnell Santosh KC Jinghua Guo Kyeongjae Cho Robert M. Wallace Ali Javey 10.1021/nn5047844.s001 https://acs.figshare.com/articles/journal_contribution/Air_Stable_p_Doping_of_WSe_sub_2_sub_by_Covalent_Functionalization/2241469 Covalent functionalization of transition metal dichalcogenides (TMDCs) is investigated for air-stable chemical doping. Specifically, p-doping of WSe<sub>2</sub> <i>via</i> NO<sub><i>x</i></sub> 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<sub>2–<i>x</i>–<i>y</i></sub>O<sub><i>x</i></sub>N<sub><i>y</i></sub> species both on the surface and interface between layers upon chemisorption reaction. <i>Ab initio</i> simulations corroborate our spectroscopy results in identifying the energetically favorable complexes, and predicting WSe<sub>2</sub>:NO at the Se vacancy sites as the predominant dopant species. A maximum hole concentration of ∼10<sup>19</sup> cm<sup>–3</sup> is obtained from XPS and electrical measurements, which is found to be independent of WSe<sub>2</sub> thickness. This degenerate doping level facilitates 5 orders of magnitude reduction in contact resistance between Pd, a common p-type contact metal, and WSe<sub>2</sub>. More generally, the work presents a platform for manipulating the electrical properties and band structure of TMDCs using covalent functionalization. 2014-10-28 00:00:00 transition metal dichalcogenides XAS XPS hole concentration WSe 2 Se vacancy sites TMDC spectroscopy Covalent FunctionalizationCovalent functionalization Ab initio simulations WSe 2 thickness