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Optical Atomic Force Sensor

IP.com Disclosure Number: IPCOM000035780D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Bartha, J: AUTHOR [+5]

Abstract

Topographies and force distributions across a surface are measured with great accuracy by scanning the surface by means of a measurement head combining the principles of atomic force microscopy (AFM), as described by G. Binnig et al. in Phys . Rev . Letters 56, 9, pp. 930-933 (March 1986), with an optical Fabry-Perot interferometer and two closed control loops.

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Optical Atomic Force Sensor

Topographies and force distributions across a surface are measured with great accuracy by scanning the surface by means of a measurement head combining the principles of atomic force microscopy (AFM), as described by G. Binnig et al. in Phys . Rev . Letters 56, 9, pp. 930-933 (March 1986), with an optical Fabry-Perot interferometer and two closed control loops.

In the figure, the surface of probe 2, supported by a piezoelectric element 1, is scanned by the tip of a micromechanical lever 3 arranged in close proximity. By a further piezoelectric element 4, lever 3 is attached to a glass block 5 such that distance d can be controllably varied. Glass block 5 comprises an internal beam splitter to direct the output beam 8 of solid-state laser 7 to the upper surface of lever 3 from which it is reflected to reach photodetector 9. The gap between glass block 5 and lever 3 (with reflecting metallic layers 6b and 6a, respectively, and suitable optical windows) acts as a Fabry- Perot interferometer which varies the intensity of the reflected beam 8 when the tip of lever 3 is attracted by atomic forces to the surface of probe 2. Metallic layers 6a and 6b also act as a capacitor, by means of which an electrostatic force can be applied to lever 3 for counteracting the attractive atomic forces. An "electric" closed-loop control circuit 11 receives the tunnelling current jT, flowing through the tip of lever 3, and acts on capacitor 6a, b and piezoelectric elements 1 and 2. An "optical" closed loop control circuit 10 receives the signal of photodetector 9 and outputs control signals for capacitor 6a, b and piezoelectric elements 1 and 2.

If the distribution of atomic forces on probe 2 is constant, the top...