A shear force feedback control system for near-field scanning optical microscopes without lock-in detection

Review of Scientific Instruments

Volumn 68, Issue 8, 1997, Pages 3093-3095

  Hsu, J W P ^a   McDaniel, A A ^a   Hallen, H D ^b  

^a University of Virginia ^*  (United States)

^b NORTH CAROLINA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000040902     PISSN: 00346748     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.1148247     Document Type: Article

References (11)

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3. M. Lee, E. B. McDaniel, and J. W. P. Hsu, Rev. Sci. Instrum. 67, 1468 (1996).
4. J. Barenz, O. Hollricher, and O. Marti, Rev. Sci. Instrum. 67, 1912 (1996).
5. A. Drabenstedt, J. Wrachtrup, and C. von Borczyskowski, Appl. Phys. Lett. 68, 3497 (1996).
6. Y.-H. Chuang, C.-J. Wang, J. Y. Huang, and C.-L. Pan, Appl. Phys. Lett. 69, 3312 (1996).
7. P. Horowitz and W. Hill, The Art of Electronics, 2nd ed. (Cambridge University Press, Cambridge, 1989).
8. feedback) and is stable if the op-amp is fast enough. We chose to use an OP-270 to minimize drift; temperature coefficients between the two op-amps on the same chip are closely matched, resulting in much smaller drift compared to using two separate single op-amps.
9. The AD636 is used in the standard configuration as given on page 4-18 of Special Linear Reference Manual published by Analog Devices.
10. 0 = 80 kHz, we obtain a settling time 5τ of 2 ms. Therefore, the feedback circuit bandwidth only needs to be a few hundred Hz.
11. We can routinely balance the bridges better and observe a smaller drift with capacitors than with the piezo/tip on the tip resonance. The difference lies in that we operate the shear force feedback at the resonant frequency of the piezo/tip electromechanical system, whereas the impedance-equivalent capacitors have no resonances in this frequency regime. Near the resonances, both the magnitude and the phase of the ac impedance vary rapidly as a function of frequency (see Ref. 2). On the contrary, the ac impedance of the capacitors is a slowly varying function.