Abstract Non-contact mode of atom force microscopy (AFM) is used in detecting the surface potential of doping ZnO. Using the scanning Kelvin probe microscopy technique, we can get the two dimensional profile of surface potential of the sample. We could determine the region under the probe is either p-type or n-type doped ZnO by comparing the relative light and shade contrast, i.e. the relative height of surface potential, on the image. Thus a simple and economical qualitative method is established.
