Analytical evaluation of tapping mode atomic force microscopy for chemicalimaging of surfaces

Scanning probe methods like atomic force microscopy (AFM) and related techn iques are promising candidates for morphological, physical, and chemical ch aracterization of surfaces on the sub-micrometer scale. In order to evaluat e the analytical potential of tapping mode AFM for obtaining material speci fic information on surface structures along with topography, we have studie d the influence of various experimental parameters on height and phase cont rast using self-assembled monolayers (SAMs) as well defined model systems. The organic films were deposited onto silicon substrates starting from alky ltrichlorosilanes with methyl-, ester-, and hydroxyl-end groups, respective ly. As a result it was found that reproducibility suffers from the fact tha t even small changes in parameters determining the force interaction betwee n tip and sample can lead to pronounced changes in image contrast. Neverthe less it has been possible to identify comparatively stable regions for the imaging parameters allowing to distinguish different sample systems by thei r specific pattern of height and phase contrasts, which can be seen as a va luable analytical contribution towards sub-micrometer chemical imaging with scanning probe microscopy. (C) 2001 Elsevier Science B.V. All rights reser ved.