A new detection system for extremely small vertically mounted cantilevers
- 12 August 2008
- journal article
- Published by IOP Publishing in Nanotechnology
- Vol. 19 (38), 384002
- https://doi.org/10.1088/0957-4484/19/38/384002
Abstract
Detection techniques currently used in scanning force microscopy impose limitations on the geometrical dimensions of the probes and, as a consequence, on their force sensitivity and temporal response. A new technique, based on scattered evanescent electromagnetic waves (SEW), is presented here that can detect the displacement of the extreme end of a vertically mounted cantilever. The resolution of this method is tested using different cantilever sizes and a theoretical model is developed to maximize the detection sensitivity. The applications presented here clearly show that the SEW detection system enables the use of force sensors with sub-micron size, opening new possibilities in the investigation of biomolecular systems and high speed imaging. Two types of cantilevers were successfully tested: a high force sensitivity lever with a spring constant of 0.17 pN nm(-1) and a resonant frequency of 32 kHz; and a high speed lever with a spring constant of 50 pN nm(-1) and a resonant frequency of 1.8 MHz. Both these force sensors were fabricated by modifying commercial microcantilevers in a focused ion beam system. It is important to emphasize that these modified cantilevers could not be detected by the conventional optical detection system used in commercial atomic force microscopes.Keywords
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