A new method for improving the accuracy of SPM and its application to AFM in liquids

Wei Gao, Michinao Nomura, Hyun Kyu Kweon, Toru Oka, Qinggang Liu, Satoshi Kiyono

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


In this paper presents an accurate AFM used in liquid that is free from the Z-directional distortion of a servo actuator is described. Two correction methods are employed in this AFM. One is the external-monitoring method, and the other is the in situ self-calibration method. The external-monitoring method is based on the fact that PZT actuators from the same class show similar hysteresis patterns. The same voltage signal used to control the servo actuator is applied to another PZT actuator which is termed the reference actuator. The displacement of the reference actuator is measured by a displacement sensor. As a result, the distortion of the AFM image can be corrected satisfactorily. In the in situ self-calibration method, the derivative of the calibration curve function of the PZT actuator is calculated from the profile measurement data sets which are obtained by repeating measurements after a small Z-directional shift. Input displacement at each sampling point is approximately estimated first by using a straight calibration line. The derivative is integrated with reference to the approximate input to obtain the approximate calibration curve. Then the approximation of the input value of each sampling point is improved using the obtained calibration curve. Next the integral of the derivative is improved using the newly estimated input values. As a result of repeating these improving process, the calibration curve converges to the correct one, and the distortion of the AFM image can be corrected. Principles and experimental results of the two methods are presented.

Original languageEnglish
Pages (from-to)877-883
Number of pages7
JournalJSME International Journal, Series C: Mechanical Systems, Machine Elements and Manufacturing
Issue number4
Publication statusPublished - 1999 Dec


  • AFM in Liquid
  • Image Distortion
  • In Situ Calibration
  • Linearity Error
  • Measurement
  • Monitoring Method
  • PZT element
  • Self-calibration
  • Shape Measurement
  • Z-direction


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