Surface potential measurements using the Kelvin probe force microscope

The Kelvin probe force microscope (KFM) can measure both the surface potential and the topographic image simultaneously without contacting the sample surface. Furthermore, both conducting and non-conducting thin layers can be measured directly with a millivolt range potential resolution and a sub-micrometer lateral resolution. In this paper, we report two improvements on the KFM which entail a new method of controlling the tip-sample distance to obtain accurate surface potentials, and a new method for increasing the topographic lateral resolution. With these improvements, we can obtain a potential resolution that is less than 1 mV and a lateral resolution of about 10 nm. Also, we report some potential measurements on Langmuir-Blodgett thin films.