Energy dissipation above plane terraces of a model crystal in non-contact atomic force microscopy
Journal of Physics: Condensed Matter
We re-examine the calculation of the dissipation energy in the non-contact atomic force microscope for a model flat surface within the stochastic friction force (the 'Brownian motion') mechanism. All important aspects of the problem are taken into account. In particular, we have considered for the first time: (i) the effect of the tip on the surface atom vibrations including the possibility of inducing local vibrational modes and (ii) the second term in the expansion of the fluctuating
... luctuating tip-surface force in atomic displacements. We found that generally, if the tip does not come very close to the surface, the first effect noticeably reduces the dissipation energy, while the second-order correction is very small, at least for the model planar surface considered. However, if during its oscillations the tip comes closer than a certain critical distance to the surface, a local vibrational mode is induced which may considerably increase the dissipation energy depending on its lifetime, i.e. the degree of anharmonicity in the system coupling the local mode (LM) with the rest of the phonons. For certain systems which provide long-living LMs, this effect may serve as a microscopic mechanism of energy dissipation. We also demonstrate that the dissipation power increases with the tip oscillation amplitude.