DISTANCE DEPENDENCE OF THE NACL(100) AFM IMAGES

Constant-altitude AFM images of the NaCl(100) surface are calculated from a fully relaxed molecular-mechanic approach using a diamond tip apex. Three different ranges of the z tip-apex-to-surface distance have been found. For 2.5 angstrom < z < 5 angstrom, the apparent corrugation is recorded from the normal force component. For intermediate z (1.4 angstrom < z < 2.5 angstrom), a surface image can be formed by measuring the lateral force because the normal corrugation decreases due to surface deformation. At even smaller distances (z < 1.4 angstrom), a contrast reversal phenomenon occurs just before the surface destruction.