High-Resolution Capacitance Measurement By Force Microscopy: Application To Sample Characterization And Potentiometry

We demonstrate the usefulness and high sensitivity of the atomic force microscope (AFM) for imaging surface dielectric properties and for potentiometry through the detection of electrostatic forces. The attractive force with an applied voltage between tip and sample is generally much larger than the van der Waals force. On the other hand, electric forces as small as 10-10 N have been measured, corresponding to a capacitance of 10-19 farad. The sensitivity of our AFM should ultimately allow us to detect capacitances as low as 8 × 10-22 farad. We have used this technique to detect the presence of dielectric material over Si, and have made measure-ments of the voltage over a p-n junction with sub-micron spatial resolution. © 1988 SPIE.