Capacitance measurements on small parallel plate capacitors using nanoscale impedance microscopy

Capacitance values in the picofarad to femtofarad range have been measured on a set of square parallel plate capacitors using a homemade nanoscale impedance microscopy (NIM) device and compared with numerical simulations. A simple analytical model involving the main geometrical parameters is proposed, which correctly fits the experimental results. This model was validated by further measurements on rectangular electrodes and capacitors surrounded by guard rings. The edge effects and stray capacitance contribution were hence determined. Finally, the present resolution of our NIM device was estimated by imaging a tiny 8×8μm2 capacitor, confirming the relevance of such reference samples.