title: Chemically-doped graphene with improved surface plasmon characteristics: an optical near-field study.
abstract: One of the most fascinating and important merits of graphene plasmonics is their tunability over a wide range. While chemical doping has proven to be a facile and effective way to create graphene plasmons, most of the previous studies focused on the macroscopic behaviors of the plasmons in chemically-doped graphene and little was known about their nanoscale responses and related mechanisms. Here, to the best of our knowledge, we present the first experimental near-field optical study on chemically-doped graphene with improved surface plasmon characteristics. By using a scattering-type scanning near-field optical microscope (s-SNOM), we managed to show that the graphene plasmons can be tuned and improved using a facile chemical doping method. Specifically, the plasmon interference patterns near the edge of the monolayer graphene were substantially enhanced via nitric acid (HNO3) exposure. The plasmon-related characteristics can be deduced by analyzing such plasmonic fringes, which exhibited a longer plasmon wavelength and reduced plasmon damping rate. In addition, the local carrier density and therefore the Fermi energy level (EF) of graphene can be obtained from the plasmonic nano-imaging, which indicated that the enhanced plasmon oscillation originated from the injection of free holes into graphene by HNO3. These findings were further corroborated by theoretical calculations using density functional theory (DFT). We believe that our findings provide a clear nanoscale picture on improving graphene plasmonics by chemical doping, which will be helpful for optimizing graphene plasmonics and for elucidating the mechanisms of two-dimensional light confinement by atomically thick materials.
authors: State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275, China. chenhj8@mail.sysu.edu.cn stsdsz@mail.sysu.edu.cn.
authors: Zebo
authors: Z
authors: Zheng
authors: Weiliang
authors: W
authors: Wang
authors: Teng
authors: T
authors: Ma
authors: Zexiang
authors: Z
authors: Deng
authors: Yanlin
authors: Y
authors: Ke
authors: Runze
authors: R
authors: Zhan
authors: Qionghui
authors: Q
authors: Zou
authors: Wencai
authors: W
authors: Ren
authors: Jun
authors: J
authors: Chen
authors: Juncong
authors: J
authors: She
authors: Yu
authors: Y
authors: Zhang
authors: Fei
authors: F
authors: Liu
authors: Huanjun
authors: H
authors: Chen
authors: Shaozhi
authors: S
authors: Deng
authors: Ningsheng
authors: N
authors: Xu