Transmission and reflection mode scanning microwave microscopy (SMM): Experiments, calibration, and simulations

Reflection mode scanning microwave microscopy (SMM) is compared to a newly developed transmission mode imaging hardware for extended scattering S11 and S12 measurements. Transmission mode imaging is realized by an SMA connector placed below the sample to excite an electromagnetic wave towards the cantilever acting as nanoscale-sized receiver structure. The frequency response was investigated between 1-20 GHz and a circuitry model of the SMM matching network was combined with a 3D finite element model of the tip-sample system. Modeling results include the local 3D electric field distribution around the nanoscale cantilever tip in contact to the sample. Reflection mode measurements were calibrated using a simple three error-parameter workflow allowing for quantitative impedance and capacitance imaging. A qualitative agreement was obtained between measurements and SMM models for both S11 and S12.