Quantitative microwave evanescent microscopy

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Abstract
We have developed a scanning evanescent microwave microscope with shielded tip geometry allowing quantitative characterization of the electrical impedance of insulating and conducting materials. By modeling the tip–sample capacitance, quantitative estimates of the sample (both dielectric and conducting) electrical impedance (real and imaginary) and tip–sample separation can be made. Measurements of the tip–sample capacitance versus tip–sample separation have been made and agree with estimated values. Also, the slope of the tip–sample capacitance with respect to the tip–sample distance is calculated to implement tip–sample distance regulation for dielectric materials.