Probing the Chemical Composition and Work Function of Suspended Reduced Graphene Oxide Membranes under Controlled Humidity Conditions
Jan Sebastian Dominic Rodriguez1*, Takuji Ohigashi2, Chi-Cheng Lee1, Meng-Hsuan Tsai1, Chueh-Cheng Yang3,4, Chia-Hsin Wang3, Chi Chen5, Way-Faung Pong1, Hsiang-Chih Chiu6, Cheng-Hao Chuang1
1Department of Physics, Tamkang University, New Taipei City, Taiwan
2Institute for Molecular Science, Okazaki, Japan
3National Synchrotron Radiation Research Center, Hsinchu, Taiwan
4Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
5Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
6Department of Physics, National Taiwan Normal University, Taipei, Taiwan
* Presenter:Jan Sebastian Dominic Rodriguez,
Electrochemical reduction of graphene oxide (GO) has emerged to be an alternative route to producing reduced GO (rGO) membranes. In our previous work, we were able to grow rGO flakes suspended on Au mesh with interesting patterns formed by distinct differences in oxidation when observed under scanning electron microscopy. Using Kelvin probe force microscopy, the same pattern of rGO was also observed for the diversity of work functions ranging from 5.55 to 5.70 eV compared with the uniform distribution of GO of 5.78 eV. Moreover, scanning transmission X-ray microscopy shows the chemical composition coordination mixing of C-OH, C-O-C, HO-C=O, and C=O bonds at nanoscale resolution. Density functional theory calculations ascribed the work function values to the diversity of functional groups, with dependence on the number of O atoms. Controlling the work function holds great significance for photovoltaic behavior and band alignment in photoelectric devices. In our present work, we probe the effect of the presence of water layers on the wide range of work function of rGO at nanoscale, which is of prime importance in elucidating the mechanism of water adsorption on GO, and is significant in applications for dehumidification and ion separation.

Keywords: suspended graphene oxide, kelvin probe force microscopy, surface potential, water adsorption