Thermal Oxidation of WSe2 Nanosheets Adhered on SiO2/Si Substrates

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• 作者：Yingnan Liu ; Cheng Tan ; Harry Chou ; Avinash Nayak ; Di Wu ; Rudresh Ghosh ; Hsiao-Yu Chang ; Yufeng Hao ; Xiaohan Wang ; Joon-Seok Kim ; Richard Piner ; Rodney S. Ruoff ; Deji Akinwande ; Keji Lai
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：August 12, 2015
• 年：2015
• 卷：15
• 期：8
• 页码：4979-4984
• 全文大小：384K
• ISSN：1530-6992

文摘

Because of the drastically different intralayer versus interlayer bonding strengths, the mechanical, thermal, and electrical properties of two-dimensional (2D) materials are highly anisotropic between the in-plane and out-of-plane directions. The structural anisotropy may also play a role in chemical reactions, such as oxidation, reduction, and etching. Here, the composition, structure, and electrical properties of mechanically exfoliated WSe₂ nanosheets on SiO₂/Si substrates were studied as a function of the extent of thermal oxidation. A major component of the oxidation, as indicated from optical and Raman data, starts from the nanosheet edges and propagates laterally toward the center. Partial oxidation also occurs in certain areas at the surface of the flakes, which are shown to be highly conductive by microwave impedance microscopy. Using secondary ion mass spectroscopy, we also observed extensive oxidation at the WSe₂鈥揝iO₂ interface. The combination of multiple microcopy methods can thus provide vital information on the spatial evolution of chemical reactions on 2D materials and the nanoscale electrical properties of the reaction products.