We report here the characterization of graphene at microwave frequencies using an improved on-wafer calibration method which did not require 50 Ω loads. Multi-layer graphene films about 3 nm thick were grown on Ni-coated Si wafers using TCVD. Co-planar transmission lines of dimension 250 μm × 30 μm were constructed from the graphene films. Scattering parameters up to 20 GHz were measured using on-wafer probes, and SOLT (short-open-load-thru), LRM (load-reflect-match) and TRL (thru-reflect-line) on-wafer calibration methods were used to enable comparison. The microwave properties were modeled by a physics-based resistor-inductor-capacitor (RLC) lumped element equivalent circuit, frm which the conductivity of bi-layer and multi-layer graphene was extracted. Our study showed modeling using TRL is more accurate, and the conductivity of graphene extracted from our model was found to be 3.2 ×104 S/m, which is better than those reported by others. Our work revealed improved graphene characterization at high frequencies since a better calibration was used here.
Z. Awang, M. H. Kara, and N. A. A. Rahim, "Microwave characterization of graphene using an improved on-wafer calibration method," Proc. SPIE 10597, Nano-, Bio-, Info-Tech Sensors, and 3D Systems II, 105970E (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 06, 2018; Published: 23 March 2018); https://doi.org/10.1117/12.2294506.
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