Modeling Graphene Contrast on Copper Surfaces Using Optical Microscopy

Report No. ARL-TR-7134
Authors: Travis M Tumlin; Mark H Griep; Emil Sandoz-Rosado; Shashi P Karna
Date/Pages: October 2014; 20 pages
Abstract: Since the discovery of graphene in 2004, extensive research has been performed to investigate uses for its excellent thermal, mechanical, and electrical properties. Top-down approaches such as mechanical exfoliation and chemical reduction along with bottom-up approaches such as chemical vapor deposition and molecular beam epitaxy are techniques that have been used to synthesize graphene and other 2-dimensional materials. Determining whether graphene has been successfully synthesized often requires transfer to a support substrate such as glass or SiO2. During the transfer process, tears and impurities can be introduced, thus reducing the quality. In the present work, graphene has been imaged using confocal laser scanning microscopy and broadband optical microscopy. This technique allows graphene to be imaged directly on the copper substrate, thus eliminating the requirement for transfer. Atomic force microscopy was used to determine copper oxide thickness, and a Matlab model based on Fresnel theory was used to determine graphene contrast as a function of excitation wavelength. Different excitation wavelengths were used to determine the validity of the model over a wide range of the visible spectrum.
Distribution: Approved for public release
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Last Update / Reviewed: October 1, 2014