Continuous monitoring of tip radius during atomic force microscopy imaging

Abstract

We present a continuous tip monitoring method during atomic force microscopy imaging based on the use of higher harmonics, which are generated in the repulsive regime as a result of the nonlinear interactions between the cantilever tip and the surface under study. We have applied this method to commercial rectangular microfabricated silicon cantilevers with force constants in the 45 N/m range and fundamental frequencies in the 300-400 kHz range and with tip radii below 10 nm. We have focused in the resonance of the 2nd flexural mode and the 6th harmonic using polystyrene surfaces. The simultaneous acquisition of topographic and higher harmonic images allows a continuous control of the state of the tip. The experimental results have been rationalized with computer simulations taking into account both the cantilever dynamics and the tip-surface interactions.