Large-area Metrology of CVD-grown Graphene Layers on Copper Foil Substrates
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Large-area Metrology of CVD-grown Graphene Layers on Copper Foil Substrates Dennis L. Pleskot1, Jennifer R. Kyle2, Maziar Ghazinejad3, Shirui Guo4, Isaac Ruiz2, Mihrimah Ozkan2, and Cengiz S. Ozkan3 1
Materials Science and Engineering Program, University of California Riverside, CA 92521, USA
2
Department of Electrical Engineering, University of California Riverside , CA 92521, USA
3
Department of Mechanical Engineering and the Materials Science and Engineering Program, University of California Riverside, CA 92521, USA
4
Department of Chemistry, University of California Riverside, CA 92521, USA
ABSTRACT Fluorescence Quenching Microscopy has been shown to be an effective means of characterizing graphene on the macroscale. Centimeter-scale CVD-grown pristine and doped graphene were manufactured in a high temperature (1000°C) furnace on pristine copper substrates. The copper was then etched away in a FeCl3 solution and the graphene was coated with DCM-based fluorescent dye before being imaged in a fluorescence microscope. The fluorescence image was then image-processed using modified Matlab software. The resulting image showed clear contrast between the pristine graphene sheet and defects on the graphene surface, which revealed that fluorescence microscopy could determine the quality of a large region of graphene. Also, significant contrast was identified between single-layer and multilayer regions, showing that this technique is also effective at determining the degree of uniformity within a graphene sample. Lastly, the fluorescence images showed contrast between doped and undoped regions of graphene. INTRODUCTION Graphene has recently been shown to consist of a variety of useful and interesting physical properties. Graphene has been shown to be over 100x stronger than steel[1], has an electron mobility of 15000 cm2V−1s−1[2], a thermal conductivity of (4.84±0.44) ×103 to (5.30±0.48) ×103 Wm−1K−1[3], and is highly transparent, only transmitting 2.3% of incident light[4]. These properties have made graphene very attractive for a variety of applications including computer electronics, solar cell devices, and high-energy supercapacitors[5]. Because of this high-performance and versatility, characterization of individual graphene sheets is highly important. Many techniques currently exist for characterization of graphene, yet nearly all of them are insufficient to effectively characterize graphene sheets that are large enough to be used in the above applications. Raman spectroscopy is a common characterization technique, yet this method can only characterize a material within a very small area, which may not be representative of the sample as a whole. Other techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) can give atomic resolution of the
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graphene surface, yet because of this high resolution, large samples cannot be imaged within a reasonable amount of time. Also, these characterization methods involve high-energy electrons that usually damage the surface of the
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