  We suggest simple model of image formation in atomic force microscope (AFM)
taking into account contact deformations of probe and sample during scanning.
The model explains the possibility of AFM visualization of regular atomic or
molecular structure when probe-sample contact area is greater than an area per
atom or molecule in surface lattice. (This is usually the case when lattice to
be studied has subnanometer unit cell parameters and AFM investigations are
carried out in air in contact mode). Two special peculiarities of AFM
visualization of two-dimensional lattice could be observed under such
conditions: 1) the inversion of contrast of AFM images, and 2) visualization of
"false atom" under single atomic vacancy of surface studied.
