ANALYSIS OF THE AMPLITUDE AND PHASE RESPONSE OF THE MICRO CANTILEVER IN THE TAPPING MODE ATOMIC FORCE MICROSCOPY

In this paper, the amplitude and phase response of the microcantilever in the tapping mode atomic force microscopy is investigated as a function of excitation frequency, free oscillation amplitude, and tip-sample separation distance. For this purpose, the influence of the excitation frequency on the transition occurring in the amplitude-phase-separation curves is analyzed by taking into consideration, three vibration modes. The obtained results show that at the excitation frequency close to resonance, the participation of higher modes in the response is negligible, and accounting for only one mode in the response is sufficient. Moreover, increasing the excitation frequency a little over the resonance frequency causes the shifting of the transition location toward smaller separation distances and finally to no separation; while, lowering the excitation frequency around the resonance results in the displacement of the jump's location toward larger separation distances. To investigate the influence of the free oscillation amplitude on transition, the share of only one mode in the response is considered. The results indicate that, depending on the value of the free oscillation amplitude, the jump either has a steplike discontinuous shape or a smooth continuous one. Also, by increasing the free oscillation amplitude, the transition occurs at a larger separation.