研究目的
To improve the performance of low-power consumption NDIR methane gas sensors by using customized optical thin film bandpass filters, enhancing signal-to-noise ratio and minimizing cross-talk, with a focus on room temperature deposition and environmental stability.
研究成果
The study successfully demonstrated that multilayer thin film bandpass filters deposited via a novel microwave plasma-assisted sputter process enhance NDIR methane sensor performance by improving signal-to-noise ratio and reducing cross-talk from water vapor. The 300 nm bandwidth filter showed better SNR, while the 160 nm filter offered reduced sensitivity to humidity. Coating uniformity and environmental stability were confirmed, indicating potential for mass production. Future work should address scalability and further mechanical testing.
研究不足
The method of applying coatings using precision masking may not be optimal for scalable mass production. The unpolished surface of the photodiode may lead to light scattering, affecting filter performance. Small sample sizes in some tests could influence noise calculations. The study focuses on methane detection and may not generalize to other gases without further optimization.
1：Experimental Design and Method Selection:
The study involved designing and depositing multilayer thin film bandpass filters using a microwave plasma-assisted pulsed DC sputter deposition process. Optical designs were modeled using TFCalc software and Mathcad for sensor performance simulation.
2：Sample Selection and Data Sources:
Samples included Gas Sensing Solutions Ltd. NDIR gas sensor photodiodes, silicon and gallium arsenide witness pieces, and methane gas mixtures for testing. Data on optical constants and gas absorption were sourced from FTIR measurements and the HITRAN database.
3：List of Experimental Equipment and Materials:
Equipment included a microwave plasma-assisted sputter reactor, FTIR spectrometers (Nicolet iS-50 and Bruker VERTEX 80/80v), mass flow controllers, environmental chambers, and pressure cookers. Materials included germanium and niobium sputtering targets, argon and oxygen gases, and various substrates.
4：Experimental Procedures and Operational Workflow:
The process involved depositing Ge and Nb2O5 layers onto photodiodes and witness samples, measuring optical transmittance, testing gas sensor responses to methane concentrations, and evaluating environmental stability through humidity, temperature, and pressure cooker tests.
5：Data Analysis Methods:
Data were analyzed using Mathcad for sensor modeling, TFCalc for optical design, and statistical methods for noise and uniformity calculations.
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