SIMULATION OF TIP-SAMPLE INTERACTION IN THE ATOMIC-FORCE MICROSCOPE

Recent simulations of the interaction between planar surfaces and mode l atomic force microscope (AFM) tips have suggested that there are con ditions under which the tip may become unstable and 'avalanche' toward the sample surface. Here we investigate via computer simulation the s tability of a variety of model AFM tip configurations with respect to the avalanche transition for a number of fee metals. We perform Monte Carlo simulations at room temperature using the equivalent-crystal the ory (ECT) of Smith and Banerjea. Results are compared with recent expe rimental results as well as with our earlier work on the avalanche of parallel planar surfaces. Our results on a model single-atom tip are i n excellent agreement with recent experiments on tunnelling through me chanically controlled break junctions.