A near-field scanning microwave microscope for measurement of the permittivity and loss of high-loss materials

The design and calibration of a Near-Field Scanning Microwave Microscope (NSMM) for measurement of permittivity and loss on the small scale are described. The instrument described uses a wire probe that is electromagnetically coupled to a resonant cavity. Using an electrostatic model based on image charges (Gao and Xiang 1998) permittivity and loss may be determined. The paper describes progress in two specific areas: (i) The implementation of an optical beam-deflection method for obtaining contact mode between the probe tip and specimens. (ii) Improvements to the calibration process to improve the traceability and accuracy of the measurement of loss by using the Laplacian ‘complex frequency’ in the image-charge model. This is demonstrated by measurements on polar liquids.