piezoresponse force microscopy vector piezoresponse force microscopy vector PFM CHMO:0000940 Microscopy where an electric field is applied to a sharp spike (known as a 'tip') which is mounted on the end of a cantilever. The tip scans the surface of a piezoelectric specimen and the distortion of the electric field by the specimen is measured as components from three directions (one vertical and two lateral). A feedback loop is used to maintain a fixed relationship between the tip and surface during scanning. VPFM