We present a design study aimed at fabricating micromachined
thermal emitters for infrared NDIR gas sensor with high emission efficiency in the
9-12 μm wavelength range.
In order to achieve high optical radiance with relatively
low power consumption and possibility of fast thermal modulation, a technology
based on dielectric membranes composed by stacked silicon oxide and nitride
with platinum heaters is adopted, that guarantees good thermal isolation and
reduced thermal mass.
The dielectric stack adopted is composed in such a way that
its emissivity is enhanced in the wavelength range of concern and an optimized
design of the emitter geometry is proposed based on finite element thermal
simulations. Some preliminary experimental results are presented about the
optical properties of the structural layer and its medium-term reliability when
operated with Pt heaters at a temperature around 600°C.
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