|
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.
|
