In order to acquire a deeper understanding of interactions between objects on the nanometer scale, the development of new scientific techniques and methods is of central significance. A comprehensive understanding of frictional aspects on this scale helps to pave the way towards innovative material developments.Friction on the nanometer scale is experimentally accessible since the advent of friction force microscopy (FFM) by Mate et al. in 1986. A fine tip at one end of a microscopically small cantilever touches a sample surface and lateral forces lead to deflections of the lever beam which are directly linked with static friction interactions between atoms.This thesis focuses on a further experimental approach which is referred to as dynamic friction force microscopy (dynamic FFM). A lateral sample modulation combined with dynamic frictional interactions between tip and surface leads to bending or torsional oscillations of the lever, depending on the configuration. A fractional resonance excitation with a frequency below the natural eigenfrequency of the cantilever beam can lead to a non-linear oscillation state, consisting of stick and slip interactions between tip and surface.If the excitation amplitude remains small, this causes a linear response where the tip sticks to the surface and directly follows the modulation movement. The cantilever oscillates at the excitation frequency. As soon as the excitation amplitude exceeds a certain threshold, a non-linear tip sliding mechanism sets in, which causes oscillations of the cantilever beam at its resonance frequency.For friction imaging, a lock-in amplifier scheme detects the arising resonant frequency component, which is directly connected with the transition from static-to-sliding of the tip. A feedback approach monitors the transition amplitude and images local friction of sample surfaces. This approach provides information about frictional properties of surfaces, which can be mapped with very high sensitivity.Furthermore, this off-resonant excitation technique is extremely sensitive to subtle surface defects. Atomic discoordinations at defects lead to variations in the atomic interaction potential with surface atoms, which is also referred to as Schwoebel-Ehrlich barrier. Increased non-linear frictional tip-sample interactions at defects lead to an increased excitation of resonance oscillations. Surface steps and grain boundaries can clearly be identified and model simulations confirm a contrast mechanism.Further, the complete resonance behavior of the cantilever is analyzed by using a fast band excitation scheme. Surface elasticity and topographical cross-talk with nanoparticles can furthermore play an important role for the image contrast formation.
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