In this work we try to optimize an IR-MEMS-emitter as a source for fast NDIR (Non-dispersive infrared) measurements. NDIR sensors are state of the art for measuring gas concentrations in the Mid-infrared spectrum. However, current IR-light sources such as micro light bulbs and MIR-LEDs cannot satisfy all the requirements for modern NDIR sensors. Therefore MEMS-IR-emitters are the only suitable source.
Time dependent measurements require a pulsed sensor operation. Industrial users expect measurement frequencies of 20 Hz to 100 Hz. Current commercially available MEMS-IR-emitters already reach their usability limit at 10 to 20 Hz.
The aim of our studies is to optimize an IR-MEMS-emitter and its operating mode for high signal modulation at pulse rates about 100 Hz. After initial tests with hybrid assembled arrays of different internally manufactured emitters, more complex emitter geometrics are simulated with Comsol Multiphysics within the range of our manufacturing possibilities.
Miniaturized versions of nowadays tabletop setups will be necessary for a successful commercialization of quantum cryptography and computing. Within this contribution, we present a concept for downsizing the Hanbury Brown-Twiss configuration. The design is based on optical simulations, with the aim of finding the best compromise of detection efficiency and level of miniaturization. Since scattering effects are important for evaluating the system’s performance, a complete scattering analysis got performed.
An advanced infrared emitter, consisting of a non-periodic silicium-microstructure and a platinium-nano-composition, which enables extraordinary highly emission intensities is presented. A spectral broadband emission coefficient ε of nearly 1 is achieved. The foundation of the emitter is a MEMS hot plate design containing a high temperature stable molybdenum silicide resistance heater layer embedded in a multilayer membrane consisting of silicon nitride and silicon oxide. The temperature resistance of the silicon-platinum micro-nanostructure up to 800 °C is secured by a SiO2 protection layer. The long-term stability of the spectral behavior at 750 °C has been demonstrated over 10,000 h by FTIR measurements. The low thermal mass of the multilayer MEMS membrane leads to a time constant of 28 ms which enables high chopper frequencies. A precondition for long term stability under rough conditions is a real hermetic housing. High temperature stable packaging technologies for infrared MEMS components were developed.
We present and discuss the infrared properties of molybdenum silicide thin films, molybdenum silicide photonic crystals and the electromigration of molybdenum silicide. Magnetronsputtered and annealed molybdenum silicide layers were investigated via infrared spectral ellipsometry. Simulations of optical properties of molybdenum silicide photonic crystals [metal-insulator-metal structures] show that properties influenced by the size of the structures differ to those of widely used photonic crystals made of Ag. The infrared absorption of MIM-structures comprising of a solid molybdenum silicide layer and one molybdenum silicide layer in form of disks were simulated for different disk diameters and layer thicknesses. A first maximum of absorption (at about 2740 nm) is almost independent of the diameter of the molybdenum silicide disk. A second maximum of absorption (7120 nm -7750 nm) shows an increase of its resonance wavelength with increasing disk diameter. A third maximum of absorption (at about 11000nm) instead shows a respective decrease. In the simulations the thicknesses of the metal layers and the dielectric layer were varied. Changes in the thickness of the dielectric layer caused greater changes in the absorption spectra than changes in the thicknesses of the metal layers. For the application in thermal emitters, the knowledge of electromigration properties of molybdenum silicide layers is crucial. Investigations via accelerated tests with different acceleration factors are demonstrated for test structures. We investigated structures based on molybdenum silicide and for comparison with a well known system analogous structures made of aluminum. We find that molybdenum silicide shows considerably lower electromigration than aluminium.
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