Estudo da interação à distância entre cantiléver e amostra em microscopia de força atômica

Abstract

In the present work, we will present a theoretical and experimental approach about the long-range interaction forces between cantilever and sample, in an Atomic Force Microscope. For this, we will assume that the dynamics of a cantilever can be understood as that of a damped forced harmonic oscillator that tends to oscillate with a frequency very close to the resonance. From this treatment, we propose, then, a model that considers the effect of plane pressure waves generated by the movement of a cantilever, whose vibrations disturb the environment in which it is immersed. Initially, we used two rectangular cantilevers with natural oscillation frequencies of 150 kHz and 300 kHz oscillating in air over glass. Subsequently, the 150 kHz probe was placed in distilled water, in order to verify how the medium could affect the measurements. Therefore, we were able to show, based on the graphs of the experimentally obtained data, that these waves in fact alter the natural frequency of vibration of the cantilever, with a dependence on the tip-sample distance.