Noncontact atomic force microscopy imaging mechanism on Ag(110):: Experiment and first-principles theory

In this study, we analyze the noncontact atomic force microscopy (NC-AFM) imaging mechanism on the Ag(110) surface by experiment and ab initio theory. The experimental NC-AFM images exhibit atomic-scale resolution in the topography and dissipation signal. Interestingly, the maximum of the damping signal is between the maxima of the topography image. Comparing the geometry of the Ag(110) surface with the topography of a simulated NC-AFM image, we found that the first surface layer silver atoms are imaged as maxima in the topographic NC-AFM images. The overall structure and the corrugation height of the theoretical NC-AFM image are in good agreement with the experimental ones. Furthermore, the analysis of the short-range tip-sample interactions calculated at specific lattice sites revealed strong hysteresis effects. Our simulations also indicate that clean silicon tips might become contaminated with silver atoms during a NC-AFM experiment. Indeed, the NC-AFM experiments showed that the Ag(110) surface is difficult to image probably due to contamination of the silicon tip during the imaging process.