THE CONTRAST MECHANISM FOR TRUE ATOMIC-RESOLUTION BY AFM IN NONCONTACT MODE - QUASI-NON-CONTACT MODE

Recent studies in which single point-like defects have been detected b y AFM in non-contact mode, i.e., true atomic resolution, have been inv estigated using numerical simulations. The use of realistic interatomi c interaction parameters allows us to do numerical simulations that ar e in very good agreement with experimental data. As a result, we are a ble to ''separate'' the different forces acting between the AFM tip an d the sample surface. Calculations indicate that the force responsible for image contrast in the experimental studies is the repulsive conta ct force, and not the attractive contact force. This result remains th e same for any reasonable set of interatomic interaction parameters. ( C) 1997 Elsevier Science B.V.