Quantitative topographic imaging using a near-field scanning microwave   microscope
  We describe a technique for extracting topographic information using a scanning near-field microwave microscope. By monitoring the shift of the system's resonant frequency, we obtain quantitative topographic images of uniformly conducting metal surfaces. At a frequency of 9.572 GHz, our technique allows for a height discrimination of about 55 nm at a separation of 30 microns. We present topographic images of uneven, conducting samples and compare the height response and sensitivity of the system with theoretical expectations. 
C. P. Vlahacos, D. E. Steinhauer, S. K. Dutta, B. J. Feenstra, Steven   M. Anlage, and F. C. Wellstood