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Micromechanical Thermometer With 10-3k to 102k Range

IP.com Disclosure Number: IPCOM000062515D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Duerig, UT: AUTHOR [+3]

Abstract

This thermometer comprises an oscillating micromechanical beam 1 and a circular membrane 2, both consisting of SiO2 and arranged at a mutual distance of about 10 mm. Membrane 2 carries a gold tip 3 at its center, which forms a gap 4 of about 2 mm width with beam 1. Membrane 2 and beam 1 are mounted on a circular support 5 which rests on a conductive base 6. With the dimensions indicated in the figure, beam 1 has an eigenfrequency of about 5 kHz. It can be made to deflect towards membrane 2 by means of a deflection voltage Vd applied between gold electrodes 7 and 8, respectively coated on beam 1 and membrane 2. With Vd adjusted appropriately, gap 4 can be made small enough to permit a constant tunneling current IT to flow when a tunnel potential VT is applied between electrode 7 and tip 3.

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Micromechanical Thermometer With 10-3k to 102k Range

This thermometer comprises an oscillating micromechanical beam 1 and a circular membrane 2, both consisting of SiO2 and arranged at a mutual distance of about 10 mm. Membrane 2 carries a gold tip 3 at its center, which forms a gap 4 of about 2 mm width with beam 1. Membrane 2 and beam 1 are mounted on a circular support 5 which rests on a conductive base 6. With the dimensions indicated in the figure, beam 1 has an eigenfrequency of about 5 kHz. It can be made to deflect towards membrane 2 by means of a deflection voltage Vd applied between gold electrodes 7 and 8, respectively coated on beam 1 and membrane 2. With Vd adjusted appropriately, gap 4 can be made small enough to permit a constant tunneling current IT to flow when a tunnel potential VT is applied between electrode 7 and tip 3. This tunneling current is modulated as membrane 2 is caused to oscillate with an accurately determined amplitude Wxmod by applying an AC voltage Vmod between the lower electrode 9 on membrane 2 and base 6. Simultaneously, the tunneling current is also modulated by thermal vibrations of beam 1. Their amplitude can be expressed in terms of the thermal fluctuations of the tunneling current WITh, the modulation amplitude Wxmod, and the corresponding amplitude of the tunneling current oscillations WImod, viz.:

(Image Omitted)

Discrimination between WITh and WImod is easily done with passband filters tuned to the lowest eigenfrequen...