A fine needle stylus mounted to a three-dimensional piezo system is scanned across the sample in x-and y-direction, while a constant spacing between tip and sample, i.e., constant tip-to-sample capacitance, is maintained in z-direction. This is accomplished by vibrating the tip in z-direction at 1 kHz by typically 0.1 microns and by detecting the capacitance modulation from the shifting of the resonance of a tuned 1 GHz line. The horizontal resolution achieved so far is limited by the tip radius at about 200 nm and the vertical resolution is about 5 nm. The theoretical limits for finer tips are 7 nm and 1 nm for horizontal and vertical resolution, respectively.
Kleinknecht, H. P.; Sandercock, J. R.; and Meier, H.
"An Experimental Scanning Capacitance Microscope,"
Scanning Microscopy: Vol. 2
, Article 3.
Available at: https://digitalcommons.usu.edu/microscopy/vol2/iss4/3