Air Stable p-Doping of WSe2 by Covalent Functionalization

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• 作者：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
• 刊名：ACS Nano
• 出版年：2014
• 出版时间：October 28, 2014
• 年：2014
• 卷：8
• 期：10
• 页码：10808-10814
• 全文大小：567K
• ISSN：1936-086X

文摘

Covalent functionalization of transition metal dichalcogenides (TMDCs) is investigated for air-stable chemical doping. Specifically, p-doping of WSe₂ via NO_x chemisorption at 150 掳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鈥?i>x鈥?i>y}O_xN_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 WSe₂:NO at the Se vacancy sites as the predominant dopant species. A maximum hole concentration of 鈭?0¹⁹ cm^鈥? is obtained from XPS and electrical measurements, which is found to be independent of WSe₂ thickness. This degenerate doping level facilitates 5 orders of magnitude reduction in contact resistance between Pd, a common p-type contact metal, and WSe₂. More generally, the work presents a platform for manipulating the electrical properties and band structure of TMDCs using covalent functionalization.

Keywords:

layered materials; covalent binding; NO₂; chemisorption; doping