A Tapping-Mode Atomic Force Microscope Utilizing Optical Pickup System
Date Issued
2006
Date
2006
Author(s)
Lin, Meng-Hu
DOI
en-US
Abstract
A compact tapping-mode atomic force microscope (AFM) utilizing an optical pickup system for measuring the deflection of the probe is presented. An optical pickup head of commercial digital versatile disc read only memory (DVD-ROM) drive is applied in the measuring system. This DVD pickup replaces the quadrant photodiode and complex light path system of traditional optical-lever technique. In addition, an inertial motor composed by a piezo-actuator is used as the sample approaching mechanism and the scanner in the vertical direction. Thus, the volume of hardware structure is decreased, and the sensing variance due to temperature change will be minimized.
In order to perform advanced controller design, we propose an integrated system model including the tip-sample interaction and dynamics of the piezo-actuator for the tapping-mode AFM. Because the amplitude of the oscillating probe is the only available information, we use a loop transfer recovery (LTR) observer to estimate system states. Then, the observed-based variable structure controller is designed for enhancing system robustness and performance. From the provided experiment results, satisfactory performances of the proposed AFM system have been successfully demonstrated. The vertical scanning resolution is ±5nm and scanning speed is 4 lines per second.
Subjects
輕敲式原子力顯微鏡
光學讀取頭系統
可變結構控制器
Tapping-mode atomic force microscopy
Optical pickup head
Variable structure controller
Type
thesis
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