Interferometer based small amplitude AFM

Abstract

The defl ection of a cantilever bearing a sharp tip upon interaction with surface needs to be measured accurately in Atomic Force Microscopy. In order to enhance force sensitivity weak cantilevers (0.05 to 0.01 N/m) are used. However, there are shortcomings of AFM in terms of its measuring e ciency and range. The focus of this thesis is on the e ort to build a new instrument to overcome these shortcomings so that one is able to make linear and quantitative force measurement. This can help us to get insights in many fi elds such as the nature of protein unfolding and its free energy landscape. Integrating the technique called interferometry to our small amplitude AFM we were successful in getting a better a signal to noise ratio. We achieved sensitivity levels of 500mV/Å using this interferometer. This allows, measurement of small cantilever amplitudes of the order of few picometers. We plan to use this interferometer based small amplitude AFM for measurement of quantitative forces while protein unfolds.