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Calibrated nanoscale capacitance measurements using a scanning microwave microscope



H P. Hubner, M. Moertelmaier, Pavel Kabos, M. Fenner, C Rankl, Atif A. Imtiaz


A scanning microwave microscope (SMM) for spatially resolved capacitance measurements in the attofarad-to-femtofarad regime is presented. The system is based on the combination of an atomic force microscope (AFM) and a performance network analyzer (PNA. For the determination of absolute capacitance values from PNA reflection amplitudes, a calibration sample of conductive gold pads of various sizes on a Si)()2 staircase structure was used. Depending on the area of the gold pads and the SI0(d)2 step height, the corresponding capacitance values, as measured with the SMM, ranged from 0.1F to 22 fF at a noise level of 2 aF. The sample capacitance could be molded to a good degree as idealized parallel plates of zero resistance, with the SIO()2 dielectric sandwiched inbetween. By bringing the AFM-tip into direct contact with the SiO(d)2 staircase structure, the electrical footprint of the tip was measured, resulting in an effective tip radius of 65 nm and tip-sample capacitance of 5 aF. The quantitative capacitance values determined from the PNA reflection amplitude were compared to control measurements using an external capacitance bridge.
Review of Scientific Instruments


Hubner, H. , Moertelmaier, M. , Kabos, P. , Fenner, M. , Rankl, C. and Imtiaz, A. (2010), Calibrated nanoscale capacitance measurements using a scanning microwave microscope, Review of Scientific Instruments, [online], (Accessed April 16, 2024)
Created November 1, 2010, Updated October 12, 2021