Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 8: SYM Micro- and Nanomechanics II

MM 8.6: Talk

Monday, March 26, 2007, 16:45–17:00, H16

Modulated lateral force microscopy: an AFM tool for analysis and modification of polymer surfaces — •Heinz Sturm — BAM VI.25, Federal Institute for Materials Research, Unter den Eichen 87, D-12205 Berlin

Scanning Probe Microscopy, here Scanning Force Microscopy in the contact mode, is widely used not only to examine the 3-dimensional surface topography, but also to evaluate nano-mechanical surface properties. This contribution focuses on the tip-surface interaction due to a shear deformation, i. e., friction. During forward and backward scan with a given scanning (shear) velocity, the cantilever lateral bending (torsion) is a measure for the lateral force. Unfortunately, both scan directions must be acquired and subtracted to separate the topography cross-talk from the friction image. Superimposing a lateral displacement between tip and surface via a dither piezo, the shear deformation is sinusoidally modulated. Images of amplitude and phase shift of the dynamic cantilever torsion within a frequency range from 30 kHz up to 60 MHz are presented. Due to the fact that friction is always a dynamic process, we prefer to call this technique "Modulated Lateral Force Microscopy" (MLFM) instead of just "Dynamic Friction Microscopy". The dependence of the modulated friction from the normal force between tip and lever can be described with the Johnson-Kendall-Roberts model.