Dynamics of a vibrating tip near or in intermittent contact with a surface

We discuss the stability of the tip motion in dynamic atomic force microsco py. A nonlinear dynamics analysis shows that the tip's phase space is divid ed in two basins of attraction. A phase space diagram dominated by either b asin of attraction implies a stable motion while a substantial contribution from both basins is associated with instabilities. Because the dominance o f a given basin of attraction depends on the tip-surface interaction potent ial and separation, stable and unstable motions are intrinsic features of a n oscillating tip near or in intermittent contact with a surface.