Engineering Ultra-Low Work Function of Graphene

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• 作者：Hongyuan Yuan ; Shuai Chang ; Igor Bargatin ; Ning C. Wang ; Daniel C. Riley ; Haotian Wang ; Jared W. Schwede ; J. Provine ; Eric Pop ; Zhi-Xun Shen ; Piero A. Pianetta ; Nicholas A. Melosh ; Roger T. Howe
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：October 14, 2015
• 年：2015
• 卷：15
• 期：10
• 页码：6475-6480
• 全文大小：356K
• ISSN：1530-6992

文摘

Low work function materials are critical for energy conversion and electron emission applications. Here, we demonstrate for the first time that an ultralow work function graphene is achieved by combining electrostatic gating with a Cs/O surface coating. A simple device is built from large-area monolayer graphene grown by chemical vapor deposition, transferred onto 20 nm HfO₂ on Si, enabling high electric fields capacitive charge accumulation in the graphene. We first observed over 0.7 eV work function change due to electrostatic gating as measured by scanning Kelvin probe force microscopy and confirmed by conductivity measurements. The deposition of Cs/O further reduced the work function, as measured by photoemission in an ultrahigh vacuum environment, which reaches nearly 1 eV, the lowest reported to date for a conductive, nondiamond material.