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In this study, the vertical deflection responses of tapping mode atomic force microscope (TM-AFM) micro-cantilever tip are obtained by simulation and experiment. The results show that, under the blocking of the sample on one side, the steady-state response of the tip is still a sinusoidal form almost symmetrical about the equilibrium position. Furthermore, from the perspective of energy dissipation of the micro-cantilever system, the phases of two surfaces with different properties are simulated under different background dissipation. The result shows that eliminating partial background dissipation can increase the phase contrast between the two surfaces. These results are of significance for understanding the tip response and phase optimization in TM-AFM.

The phase information reflects the energy dissipation of the probe and sample interactions in tapping mode atomic force microscopes (TM AFMs). In this paper, we use the method of tune test in TM AFM to study the contribution of external environment to energy dissipation by changing the probe position and ambient humidity. Finally, the theoretical and experimental quality factors of air viscous damping, squeeze film damping and liquid bridge force are obtained to characterise energy dissipation. The analytically predicted values of the model established on squeeze film damping, viscous damping and liquid bridge force comparing to the experimental results in this paper is rational. And the comparative analysis results show that the main mechanism of energy dissipation is different at different probe positions and different relative humidness. This result is of great significance for understanding the mechanism of phase imaging experimentally and theoretically.

Phase image in tapping mode atomic force microscope (TM-AFM) results from various dissipation in microcantilever system. The phases mainly reflected the tip-sample contact dissipations which allowed the nanoscale characteristics to be distinguished. In this research investigation, two factors affecting the phase and phase contrast were analyzed. It was concluded from the theoretical and experimental results that the phases and phase contrasts in the TM-AFM were related to the excitation frequencies and energy dissipation of the system. For a two-component blend, it was theoretically and experimentally proven that there was an optimal excitation frequency for maximizing the phase contrast. Therefore, selecting the optimal excitation frequency could potentially improve the phase contrast results. In addition, only the key dissipation between the tip and sample was found to accurately reflect the sample properties. Meanwhile, the background dissipation could potentially reduce the contrasts of the phase images and even mask or distort the effective information in the phase images. In order to address the aforementioned issues, a self-excited method was adopted in this study in order to eliminate the influencing effects of the background dissipation on the phases. Subsequently, the real phase information of the samples was successfully obtained. It was considered in this study that eliminating the background dissipation had effectively improved the phase contrast results and the real phase information of the samples was accurately reflected. These results are of great significance to optimize the phase of two-component samples and multi-component samples in atomic force microscope.