Phase Imaging is a derivative mode of Dynamic Mode AFM (both Lateral and Vertical) where the phase of the cantilever oscillations φ, measured relative to the drive signal oscillations, has turned out to be a powerful signal for studying the properties of the sample surface, especially heterogeneous surfaces. Phase Imaging has become especially useful for polymer research, and for electrical and magnetic property investigations as in Electric Force Microscopy (EFM) and Magnetic Force Microscopy (MFM).
Phase Images often compliment topography images by mapping the various regions of the sample surface each of which interact with the tip in a slightly (or signiﬁcantly) different way from each. This difference is sometimes so subtle that it is barely noticeable in the Topography Image, but clearly visible in the contrast variations in the Phase Image. More often than not, however, topographic features convolve into the Phase Image, and must be recognized apart from the contrast in the Phase Image that is primarily a result of material inhomogeneity.
Experienced users of Phase Imaging are better able to tell the difference between phase contrast due to differences in material properties from that due to topography convolution.
The origin and the interpretation of the phase signal has been the subject of intense research and debate since the early 1990s, but even so, the utility of Phase Imaging has expanded the applications of Dynamic Modes of AFM into numerous broad areas of research including magnetic and electric properties.