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Modeling Combined Thermal, Electrical, Optical and Mechanical Response for MEMS Spectroscopic Gas Sensor Based On Photonic Crystals

Published online by Cambridge University Press:  11 February 2011

Anton C. Greenwald
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
Martin U. Pralle
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
Mark P. McNeal
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
Nicholas Moelders
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
Irina Puscasu
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
James T. Daly
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
Edward A. Johnson
Affiliation:
Ion Optics, Inc., Waltham, MA 02452, USA
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Abstract

A new type of gas sensor was developed that combines the principles of bolometric infrared detectors with photonic crystals.1,2 This paper describes a quantitative model used to optimize the materials, geometry, and electrical properties of this suspended membrane MEMS device. Fundamentally the model is concerned with the thermal response of the device using temperature dependent thermal conductivity, specific heat, and electrical resistance to calculate conduction, convection, and radiation losses for a negative temperature coefficient of resistance material. Variations in the electrical drive circuit, dc and ac response, low and high frequency sinusoidal and random noise, along with an exacting calculation of expected signal were used to improve design. The model follows the time evolution of the system. We show how look-up tables with scaling (derived from exact, off-line finite element models for thermal conduction, spectral emission, etc.) provided sufficiently accurate estimates with rapid calculation to enable running the model on a standard PC type computer. The simulations matched the experimental results, accurately predicted the unstable operating regimes, and maximized the signal to noise ratio for the device.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

1. US patent 6,376,856.Google Scholar
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4. Greenwald, A.C. et al, “Narrow Band Emission From Lithographically Defined Photonic Bandgap Structures In Silicon: Matching Theory And Experiment”, MRS Symp. Proc. v637, E2.6, (2000).Google Scholar
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