title: Engineering Ultra-Low Work Function of Graphene.
abstract: 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.
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Yuan
authors.forename: Shuai
authors.initials: S
authors.lastname: Chang
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Igor
authors.initials: I
authors.lastname: Bargatin
authors.forename: Ning C
authors.initials: NC
authors.lastname: Wang
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Riley
authors.forename: Haotian
authors.initials: H
authors.lastname: Wang
authors.forename: Jared W
authors.initials: JW
authors.lastname: Schwede
authors.forename: J
authors.initials: J
authors.lastname: Provine
authors.forename: Eric
authors.initials: E
authors.lastname: Pop
authors.forename: Zhi-Xun
authors.initials: ZX
authors.lastname: Shen
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , 2575 Sand Hill Road, MS31, Menlo Park, California 94205, United States.
authors.forename: Piero A
authors.initials: PA
authors.lastname: Pianetta
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Melosh
authors.forename: Roger T
authors.initials: RT
authors.lastname: Howe
keywords: Graphene; electrostatic gating; photoemission; scanning Kelvin probe force microscopy; transistor; work function