Dissipation Mechanisms Studied by Dynamic Force Microscopies

The dissipation mechanisms of contact force microscopy on solid surfaces are related to the fast motion during the slip process. Different degrees of freedom can be excited, such as phonons or electronic excitations. The dissipation mechanisms of dynamic force microscopy (DFM) were recently investigated due to the improvement in large amplitude DFM, also called dissipation force microscopy. Experimental methods to determine damping with DFM will be discussed. When an electrical field is applied between probing tip and sample, damping is observed, which depends on voltage. This type of damping is related to mirror charges, which move in the sample and/or tip because of the motion of the cantilever. When the contact potential is compensated, this long-range part is minimized. Under these conditions, only short-range damping can be measured, which appears at distances of about lnm and increases exponentially with closer separation. Recent models of this type of damping show, that there might be a relationship to the local phonon density.