Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 54: Nanostructures at surfaces II

O 54.1: Talk

Wednesday, March 28, 2012, 16:45–17:00, MA 042

(contribution withdrawn) Dynamic AFM with reduced contact stiffness by the employment of nanowires — •Ivo Knittel, Moid Bhatti, and Uwe Hartmann — Fachrichtung Experimentalphysik, Universität des Saarlandes, 66123 Saarbrücken

Nanowire tips for atomic force microscopy, employing a nanowire or a ``supertip'' on top of a conventional AFM tip, have been found advantagous in many respects. Nanowire tips are employed for high-resolution imaging of high-aspect ratio sample features, but also in order to obtain well-defined and enhanced local fields. However, in many cases a nanowire at the tip is flexible, reducing the contact stiffness to extremely low values. The resulting effective tip-sample force-distance relation is characteristic and leads to an unusual dynamics in intermittent-contact AFM.

Nanocantilever-on-cantilever AFM tips were produced by modification of conventional silicon AFM tips by means of a focused ion beam. A second type of probes were multiwalled carbon nanotube AFM tips. In addition, the intermittent-contact interaction between a conventional AFM tip and several types of nanowires on substrates was investigated. Nanowires were freely standing with resonant frequencies between 10Mhz and 1GHz and lengths between 5μm and 300nm.

Experimental and simulated intermittent-contact distance-dependent resonance curves were compared. We show the existence of a third state of intermittent-contact cantilever dynamics besides the well-known ``low-amplitude'' and the ``high-amplitude'' states. The particular role of adhesion and dissipation is also discussed.