Nanotomography with enhanced resolution using bimodal atomic force microscopy

High resolution volume images of semicrystalline polypropylene were obtained by stepwise wet-chemical etching followed by atomic force microscopy of the specimen. Enhanced signal-to-noise ratio and spatial resolution were achieved by using the second flexural eigenmode of the cantilever for phase imaging while the amplitude of the first mode was used as feedback signal. The energy dissipated between the tip and the sample revealed characteristic differences between the crystalline and the amorphous regions of the polypropylene after etching, indicating the presence of a thin (≪10 nm thick) amorphous layer on top of crystalline regions.