Title: In-situ characterisation of the defect density in reduced graphene oxide under electrical stress using fluorescence microscopy

Authors: Zequn Zeng; Preetpal Singh; Sharon Lim Xiaodai; Cher Ming Tan; Chorng-Haur Sow

Addresses: Centre for Reliability Science and Technology, Chang Gung University, Wenhua 1st Road, Guishan Dist., Taoyuan City, 33302, Taiwan ' Centre for Reliability Science and Technology, Chang Gung University, Wenhua 1st Road, Guishan Dist., Taoyuan City, 33302, Taiwan; Department of Electronics Engineering, Chang Gung University, Wenhua 1st Rd., Guishan Dist., Taoyuan City, 33302, Taiwan ' Department of Physics, National University of Singapore, 2 Science Drive3, Singapore, 117551, Singapore ' Centre for Reliability Science and Technology, Chang Gung University, Wenhua 1st Road, Guishan Dist., Taoyuan City, 33302, Taiwan; Department of Electronics Engineering, Chang Gung University, Wenhua 1st Rd., Guishan Dist., Taoyuan City, 33302, Taiwan; Department of Urology, Chang Gung Memorial Hospital, Guishan, Taoyuan, 333, Taiwan; Department of Mechanical Engineering, Ming Chi University of Technology, 84 Gungjuan Rd., Taishan Dist., New Taipei City, 24301, Taiwan ' Department of Physics, National University of Singapore, 2 Science Drive3, Singapore, 117551, Singapore

Abstract: A new approach to characterise the defect density in graphene oxide (GO) is presented in this work. Fluorescence microscopy is employed to directly observe changes in defect density on the graphene oxide surface at the macroscopic level. The area under scan becomes darker as the electrical bias is increased from 0.5 V to 3 V. Gray level conversion of the fluorescence images is used to quantify our results. The reduction of graphene oxide as observed under fluorescence microscopy images is also verified using Raman microscopy where I_D/I_G ratio decreases as the voltage stress is increased. However, defect density increases for the samples from 0 V to 0.5 V range and is maintained till 1 V, which shows that this range may not be suitable for electronic applications when graphene oxide is employed as its electronic properties are poor in this range. Thus, this in-situ measurement of defect density on the graphene oxide for large area graphene samples can help in identifying the uniformity of the defect density on graphene oxide as well as its defect density changes under electrical bias condition, an information crucial for its electronic applications.

Keywords: In-situ characterisation; grey level conversion; Raman microscopy; macroscopic defect mapping; fluorescence microscopy; graphene oxide; defect density.

DOI: 10.1504/IJNT.2020.109350

International Journal of Nanotechnology, 2020 Vol.17 No.1, pp.57 - 70

Published online: 03 Sep 2020 *

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