Imaging micro-cracks in gold films: a comparative study of scanning tunneling and atomic force microscopies

In this work, three different scanning probe microscopy (SPM) modes, scanning tunneling microscopy, atomic force microscopy (AFM) -intermittent contact mode; and AFM-contact mode, are compared by imaging micro-cracks on a thin Au film. The excellent capability of SPM techniques to image prominences are confirmed by easily imaging Au particles. Their capabilities to image surface cavities are also analyzed, with an indication that the AFM-intermittent contact mode, using etched Silicon tips, is close to its resolution limit. These results are discussed in terms of spatial extension of the interaction and tip radius of curvature. It is also found that the AFM-contact images undergo an evolution with time producing sharper images. Several possibilities to this effect are reviewed, resulting in an indication that AFM-intermittent contact and AFM-contact images, in this case, are generated by different tip–sample interaction processes in the nanometric scale.