ATOMIC-FORCE MICROSCOPY AND REAL ATOMIC-RESOLUTION - SIMPLE COMPUTER-SIMULATIONS

Using a simple computer simulation for AFM imaging in the contact mode , pictures with true and false atomic resolution are demonstrated. The surface probed consists of two f.c.c. (111) planes and an atomic vaca ncy is introduced in the upper layer. Changing the size of the effecti ve tip and its registry with respect to the atoms of the crystal probe d, images with completely different qualitative features are obtained. If the effective tip is a single atom the vacancy is clearly imaged. However, if the tip consists of several atoms and is in registry with the sample, a virtual atom appears instead of the vacancy and the crys tal lattice is perfectly reproduced. If the tip is out of registry wit h respect to the sample, artifacts having the size of the effective ti p are reported.