title: A new detection system for extremely small vertically mounted cantilevers.
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.
authors.affiliation: H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK.
authors.forename: M
authors.initials: M
authors.lastname: Antognozzi
authors.forename: A
authors.initials: A
authors.lastname: Ulcinas
authors.forename: L
authors.initials: L
authors.lastname: Picco
authors.forename: S H
authors.initials: SH
authors.lastname: Simpson
authors.forename: P J
authors.initials: PJ
authors.lastname: Heard
authors.forename: M D
authors.initials: MD
authors.lastname: Szczelkun
authors.forename: B
authors.initials: B
authors.lastname: Brenner
authors.forename: M J
authors.initials: MJ
authors.lastname: Miles