Large Area Growth and Electrical Properties of p-Type WSe2 Atomic Layers

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• 作者：Hailong Zhou ; Chen Wang ; Jonathan C. Shaw ; Rui Cheng ; Yu Chen ; Xiaoqing Huang ; Yuan Liu ; Nathan O. Weiss ; Zhaoyang Lin ; Yu Huang ; Xiangfeng Duan
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：January 14, 2015
• 年：2015
• 卷：15
• 期：1
• 页码：709-713
• 全文大小：329K
• ISSN：1530-6992

文摘

Transition metal dichacogenides represent a unique class of two-dimensional layered materials that can be exfoliated into single or few atomic layers. Tungsten diselenide (WSe₂) is one typical example with p-type semiconductor characteristics. Bulk WSe₂ has an indirect band gap (鈭?.2 eV), which transits into a direct band gap (鈭?.65 eV) in monolayers. Monolayer WSe₂, therefore, is of considerable interest as a new electronic material for functional electronics and optoelectronics. However, the controllable synthesis of large-area WSe₂ atomic layers remains a challenge. The studies on WSe₂ are largely limited by relatively small lateral size of exfoliated flakes and poor yield, which has significantly restricted the large-scale applications of the WSe₂ atomic layers. Here, we report a systematic study of chemical vapor deposition approach for large area growth of atomically thin WSe₂ film with the lateral dimensions up to 鈭? cm². Microphotoluminescence mapping indicates distinct layer dependent efficiency. The monolayer area exhibits much stronger light emission than bilayer or multilayers, consistent with the expected transition to direct band gap in the monolayer limit. The transmission electron microscopy studies demonstrate excellent crystalline quality of the atomically thin WSe₂. Electrical transport studies further show that the p-type WSe₂ field-effect transistors exhibit excellent electronic characteristics with effective hole carrier mobility up to 100 cm² V^鈥? s^鈥? for monolayer and up to 350 cm² V^鈥? s^鈥? for few-layer materials at room temperature, comparable or well above that of previously reported mobility values for the synthetic WSe₂ and comparable to the best exfoliated materials.