Finite-element simulations of a volumetric scanning microwave probe for imaging at the nanoscale

Many electrical scanning probe microscopy (SPM) techniques suffer from parasitic stray EM field contributions, which give rise to low signal to noise ratio and make the image retrieval process more difficult. Here, we validate via computational modeling a calibration procedure that employs three calibration standards and three complex coefficients to obtain a black-box transfer function between the systemic reflection coefficient and the reflection coefficient at the tip of the probe, from which the impedance, capacitance and dielectric constant of nano-sized structures can be determined. We find that a 1^o variation in the inclination angle of the cantilever can cause a 10% variation in the bulk systemic impedance. Experimental scanning microwave microscope measurements agree with our simulation results.