Ultrathin 2D Photodetectors Utilizing Chemical Vapor Deposition Grown WS2 With Graphene Electrodes

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• 作者：Haijie Tan ; Ye Fan ; Yingqiu Zhou ; Qu Chen ; Wenshuo Xu ; Jamie H. Warner
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：10
• 期：8
• 页码：7866-7873
• 全文大小：553K
• 年卷期：0
• ISSN：1936-086X

文摘

In this report, graphene (Gr) is used as a 2D electrode and monolayer WS₂ as the active semiconductor in ultrathin photodetector devices. All of the 2D materials are grown by chemical vapor deposition (CVD) and thus pose as a viable route to scalability. The monolayer thickness of both electrode and semiconductor gives these photodetectors ∼2 nm thickness. We show that graphene is different to conventional metal (Au) electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables the photoresponsivity to be modulated by electrostatic gating and light input control. We demonstrate lateral Gr–WS₂–Gr photodetectors with photoresponsivities reaching 3.5 A/W under illumination power densities of 2.5 × 10⁷ mW/cm². The performance of monolayer WS₂ is compared to bilayer WS₂ in photodetectors and we show that increased photoresponsivity is achieved in the thicker bilayer WS₂ crystals due to increased optical absorption. This approach of incorporating graphene electrodes in lateral TMD based devices provides insights on the contact engineering in 2D optoelectronics, which is crucial for the development of high performing ultrathin photodetector arrays for versatile applications.