27 September 2012 Modeling and experimental verification of graphene co-planar waveguide transmission lines
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Abstract
In this paper we report the use of graphene for microwave integrated circuit transmission lines. Multi-layered graphene films were grown on Si wafers coated with SiO2 and Ni using chemical vapour deposition. A modified procedure to etch graphene used in our work involved the use of Au on top of graphene which formed defects by breaking bonds of the underlying graphene, but our modified procedure enabled the etching process to be performed with the presence of PMMA masking layer. The etchant was made of 3HCl:HNO3:8H2O. Co-planar transmission lines of various widths and lengths were constructed on graphene to ensure compatibility with microwave wafer probes used in the measurements. The lines and the underlying SiO2 layer were modeled using CST Microwave Studio electromagnetic simulator. The centre conductor width was 30 μm, while the spacing varied from 30 to 100 μm. The graphene parameters were subsequently subtracted out from measurements by curve-fitting the experimental results with simulation. Low frequency I-V measurements revealed conductivity of the order of 2.89 × 107 S/m, but scattering parameter measurements of the samples conducted over 1 to 20 GHz revealed much lower conductivity, an effect which we think was the result of poor quality thermally grown SiO2 substrates used in this experiment.
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Z. Awang, M. H. Kara, M. H. Amir, A. Awang Teh, M. R. Mahmood, "Modeling and experimental verification of graphene co-planar waveguide transmission lines", Proc. SPIE 8462, Carbon Nanotubes, Graphene, and Associated Devices V, 84620A (27 September 2012); doi: 10.1117/12.929503; https://doi.org/10.1117/12.929503
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