Tapping Mode Atomic Force Microscopy on Polymers: Where Is the True Sample Surface?

We investigate in detail the processes involved when soft polymeric materials are imaged with TappingMode atomic force microscopy (TM-AFM). Measuring lateral arrays of amplitude/phase vs distance (APD) curves, we are able to determine quantitatively the amount of tip indentation and reconstruct the shape of the “real” surface of the sample. Moreover, contrast inversion in height and TappingMode phase images is explained on the basis of attractive and repulsive contributions to the tip−sample interaction. The experiments are performed on surfaces of poly(styrene-block-butadiene-block-styrene) (SBS) triblock copolymers acting as a model system.