An Advanced Impedance Calibration Method for Nanoscale Microwave Imaging at Broad Frequency Range

A new calibration method for nanoscale complex impedance imaging with the scanning microwave microscope is presented, which allows to calibrate the complete frequency range in a short automated procedure. The vector network analyzer and the corresponding electronically switched calibration capabilities in combination with time domain gating and microwave network modeling are used to de-embed the full system. The entire calibration requires not more than 5 min and the acquisition of one single electrostatic force microscopy approach curve. In order to demonstrate the broadband capabilities, calibrated approach curves at various frequencies are presented. Nano-Schottky diodes on a semiconductor substrate as well as biological cells were measured to demonstrate that the sample conductance and susceptance are in agreement with the theoretical expectations for the samples. This advanced workflow of quantitative impedance calibration may have many applications in the fields of semiconductor failure analysis, 2-D materials, and biological samples in their native liquid environment.