Phase imaging as an extension to tapping mode AFM for the identification of material properties on humidity-sensitive surfaces

A method for accessing information in addition to the topography primarily provided by topping mode atomic force microscopy (TM-AFM) is presented. The phase difference between the driving signal bf the piezo oscillating the cantilever in the TM-AFM and the resulting motion of the tip is exploited in order to access additional information about the tip sample interaction. Adhesive forces between the tip and the surface can be mapped simultaneously to the topographic data with the same lateral resolution. We found evidence that the phase signal is closely related to the nature of the water layer present on surfaces exposed to the ambient atmosphere by examining aerosol particles on polyester foil and the corrosion of potash-lime-silica glass with medieval composition. However, also the topography as well as operating parameters such as load force and scan speed contribute to the phase signal making quantitative comparisons difficult.