A novel excitation scheme to enhance image resolution in dynamic atomic force microscopy

Abstract

We propose a novel multifrequency excitation technique for the non-contact atomic force microscopy (AFM). The probe is excited at two frequencies that are far from resonances while their subtraction is close to the fundamental frequency. Due to combination resonance occurring in nonlinear systems, the response includes a term with frequency equal to subtraction of excitation frequencies. We suggest to employ this term as the main signal for imaging. It is found that the present excitation improves signal sensitivity to sample topography and increases resolution. This technique is especially convenient for highly-damped environments where non-contact AFMs are very difficult to use.