Chinese Journal of Theoretical and Applied Mechanics ›› 2020, Vol. 52 ›› Issue (4): 1106-1119.DOI: 10.6052/0459-1879-20-099

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STUDY ON A DYNAMICS MODEL OF TAPPING MODE AFM AND ENERGY DISSIPATION MECHANISM$^{\bf 1)}$

Wei Zheng(),Zheng Xiaoting,Liu Jing,Wei Ruihua   

  1. College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology, Beijing 100029,China
  • Received:2020-04-02 Accepted:2020-05-02 Online:2020-07-18 Published:2020-04-28
  • Contact: Wei Zheng

Abstract:

In the tapping mode, the AFM probe experiences a continuous energy dissipation process when the probe gradually approaches the sample from a far distance to an intermittent contact. Researches on the energy dissipation mechanism of this continuous process still exists sporadically in various literatures, and there are few systematic explanations and experimental verifications for the energy dissipation mechanism of each stage in the continuous process. In this paper, a new simplified model of the AFM probe-sample system under displacement excitation is proposed, and a calculation method for the equivalent damping of the one-dimensional vibration system is obtained. By this method, the viscous damping of the air when the probe is far away from the sample surface and the air squeeze film damping when the probe is close to the sample are calculated. Finally, the change of the environmental dissipation mechanism in the process from the probe away from the sample to the intermittent contact with the sample surface is analyzed, and the relationship curve between the theoretical quality factors of the AFM system and the working positions of the probe is obtained. Based on this, the micro-cantilever frequency sweep experiments with different probes in tapping mode are carried out. The frequency sweep curves are obtained through the experiments, thus obtaining the experimental relationship curve between the quality factors of the system and the working positions of the probe. The accuracy of the theoretical model is verified from the experiments. Through theoretical analysis and experimental verification of the AFM environmental dissipation mechanism in tapping mode, a further understanding of the dynamics characteristics of tapping mode AFM and its damping mechanism will be provided by this study. At the same time, it provides theoretical reference and experimental methods for the research of the energy dissipation mechanism in Micro-nano electromechanical system (MEMS/NEMS).

Key words: atomic force microscope, dynamics model, energy dissipation, air damping, squeeze damping

CLC Number: