AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP20
Technique for Optical Lever Calibration for Surface Stress Measurements

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: P.J. Williams, McGill University, Canada
Authors: P.J. Williams, McGill University, Canada
M. Godin, McGill University, Canada
V. Tabard-Cossa, McGill University, Canada
P. Grutter, McGill University, Canada
Correspondent: Click to Email
The atomic force microscope (AFM) is increasingly being used not just to image surfaces of interest but also to probe the mechanical properties of the surface, using force spectroscopy for example. In addition, AFM cantilevers are being used as the basis of nanosensors to measure a variety of signals, including surface stress, temperature etc. In all of these applications, it is important that the relationship between the output of the position sensing detector (PSD) and the deflection of the cantilever be well known. In this poster we present a new technique for determining this relation. We attach a small resistive heater to the cantilever chip to induce a bending through the bimetallic effect. We simultaneously monitor the deflection of the beam with a fibre optic interferometer that is brought up to the backside of the cantilever and with a PSD. The interferometer fibre is positioned to be at the focus of the laser beam and hence we are measuring the deflection of the cantilever at the same position that the laser spot is focused. By computing the power spectrum of the interferometer output versus the PSD output, the PSD can be accurately calibrated. We have employed this calibration technique in a measurement of the surface stress associated with the formation of a self assembled monolayer of alkanethiol on gold.