IMAGING ELASTIC SAMPLE PROPERTIES WITH AN ATOMIC-FORCE MICROSCOPE OPERATING IN THE TAPPING MODE

Many delicate samples cannot be imaged without artefacts by contact-mo de AFM. However, tapping-mode AFM is well suited for topographic imagi ng of this kind of sample. When the delicate samples laterally consist of different material phases, ambiguities in the interpretation of th e topographic image can occur. Unfortunately, at present for tapping-m ode imaging there is no technique available for the acquisition of mat erial-contrast images. In this paper we present a way for tapping-mode material-contrast imaging. The material property utilised is the diff ering deformability of distinct material phases. Therefore, the contro lled elastic deformation of the sample in the tapping mode is the firs t investigation carried out in this study. The novel method of tapping -mode material-contrast imaging has been validated for two different k inds of samples, both consisting of hard substrates partially covered by deformable organic adsorbates. In both cases deformabilities could be measured and material-contrast images have been acquired. The small est visible adsorbed objects in the material-contrast images had a wid th of about 5 nm.