AVS 51st International Symposium
    Nanometer-scale Science and Technology Thursday Sessions
       Session NS1-ThA

Paper NS1-ThA10
Novel MEMS Devices for Accurate Lateral and Normal Force Measurement in AFM

Thursday, November 18, 2004, 5:00 pm, Room 213C

Session: Nanoscale Imaging
Presenter: P.J. Cumpson, National Physical Laboratory, UK
Authors: P.J. Cumpson, National Physical Laboratory, UK
J. Hedley, Newcastle University, UK
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The uncertainty in the spring constants of AFM cantilevers is a limiting factor in a wide range of measurements of nanoscale quantities (chemical, electrical, mechanical) at a lateral resolution of 30 nm or below. The tip/cantilever fabrication process suggests that manufacturing cantilevers to the exquisite dimensional accuracy required to produce sufficiently repeatable spring constants will always be a challenge; an easy and accurate calibration method is needed. A number of methods have been suggested for calibrating AFM cantilevers@footnote 1@, all of which have limited accuracy or are difficult to perform. We have developed a novel microfabricated device capable of calibrating AFM cantilevers for normal spring constant@footnote 2@ much more easily. The device consists of a surface micromachined silicon resonator, which can be set into resonance at an amplitude of around 10 nm in vacuum. By applying Doppler interferometry and electrical measurement simultaneously, the spring-constant of the MEMS device can be deduced, to an uncertainty of around ±2%, without physical contact. Here we present a new MEMS device for the first time, specifically designed to make lateral force constant calibration easy and accurate. This presented challenging fabrication and interferometry problems. Nevertheless, it is particularly valuable since few other options exist for quantitative measurement of lateral force. @FootnoteText@ @footnote 1@ N A Burnham et al, Nanotechnology 14 (2003) 1-6.@footnote 2@ P J Cumpson and J Hedley, Nanotechnology 14 (2003) 1279-1288.