A design of an ultra-compact infrared gas sensor for respiratory quotient (qCO2) detection

Xu, Maosen; Xu, Yan; Tao, Jifang; Li, Yan; Kang, Qiaoqiao; Shu, Dongsheng; Li, Tie; Liu, Yanxiang

doi:10.1016/j.sna.2021.112953

Cited by 19 publications

(2 citation statements)

References 15 publications

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“…To the best of our knowledge, this is the first demonstration of a functional small NDIR CO 2 gas sensor using a 20% ScAlN-based pyroelectric detector. Table shows a comparison of the size and performance of recently reported NDIR CO 2 gas sensors using broadband sources and microelectromechanical systems (MEMS) detectors for environmental monitoring, published within the past 2 years. ,,,− For NDIR gas sensors which are known for their large footprints, size reduction could bring about a compromise in the lowest detection limit and response time. This can be seen in Table by an NDIR gas sensor with lowest CO 2 detection limit reported at 2 ppm.…”

Section: Resultsmentioning

confidence: 99%

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

Liang

Chen

et al. 2022

ACS Sens.

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NDIR CO 2 gas sensors using a 10-cm-long gas channel and CMOS-compatible 12% doped ScAlN pyroelectric detector have previously demonstrated detection limits down to 25 ppm and fast response time of ∼2 s. Here, we increase the doping concentration of Sc to 20% in our ScAlN-based pyroelectric detector and miniaturize the gas channel by ∼65× volume with length reduction from 10 to 4 cm and diameter reduction from 5 to 1 mm. The CMOS-compatible 20% ScAlN-based pyroelectric detectors are fabricated over 8-in. wafers, allowing cost reduction leveraging on semiconductor manufacturing. Cross-sectional TEM images show the presence of abnormally oriented grains in the 20% ScAlN sensing layer in the pyroelectric detector stack. Optically, the absorption spectrum of the pyroelectric detector stack across the mid-infrared wavelength region shows ∼50% absorption at the CO 2 absorption wavelength of 4.26 μm. The pyroelectric coefficient of these 20% ScAlN with abnormally oriented grains shows, in general, a higher value compared to that for 12% ScAlN. While keeping the temperature variation constant at 2 °C, we note that the pyroelectric coefficient seems to increase with background temperature. CO 2 gas responses are measured for 20% ScAlN-based pyroelectric detectors in both 10-cm-long and 4-cm-long gas channels, respectively. The results show that for the miniaturized CO 2 gas sensor, we are able to measure the gas response from 5000 ppm down to 100 ppm of CO 2 gas concentration with CO 2 gas response time of ∼5 s, sufficient for practical applications as the average outdoor CO 2 level is ∼400 ppm. The selectivity of this miniaturized CO 2 gas sensor is also tested by mixing CO 2 with nitrogen and 49% sulfur hexafluoride, respectively. The results show high selectivity to CO 2 with nitrogen and 49% sulfur hexafluoride each causing a minimum ∼0.39% and ∼0.36% signal voltage change, respectively. These results bring promise to compact and miniature low cost CO 2 gas sensors based on pyroelectric detectors, which could possibly be integrated with consumer electronics for real-time air quality monitoring.

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Section: Resultsmentioning

confidence: 99%

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

Liang

Chen

et al. 2022

ACS Sens.

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“…We report here, one of the fastest gas response times compared to most NDIR CO 2 gas sensors that report gas response time is nearly tens of seconds. [ 66–68 ] So far, our experimental data have shown superiority of 12% ScAlN‐based pyroelectric detector compared to its AlN counterpart under the same measurement conditions, indicating that doping with Sc is the direction to push up device performance. Despite that, when CO 2 gas responses are fitted with modified Beer–Lambert equation, we note comparable span and κ regardless of the pyroelectric material used and sensing area of the pyroelectric material, which signifies that with the same gas, the gas channel is oblivious of the change in detector.…”

Section: Discussionmentioning

confidence: 66%

CMOS AlN and ScAlN Pyroelectric Detectors with Optical Enhancement for Detection of CO₂ and CH₄ Gases

Liang

et al. 2023

Adv Elect Materials

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Gassensors are useful for monitoring of greenhouse gases. As the move toward complementary metal-oxide-semiconductor (CMOS) compatible pyroelectric room temperature detectors is gaining traction due to its scalability to 8-in./12-in. wafer area and integrable with CMOS electronics, CMOS compatible aluminum nitride (AlN)-and scandium aluminum nitride (ScAlN)-based pyroelectric detectors are developed for sensing of CO 2 and CH 4 gases, which are two of the greenhouse gases that contribute significantly to global warming. Leveraging gas absorption at respective mid-infrared (IR) wavelengths, CO 2 and CH 4 gases are detected at various concentrations with fast response time ≈1 s. A compound parabolic collector (CPC) is designed and integrated into the gas sensor to enhance the optical flux received by the detector, which demonstrates ≈10× signal improvement in its presence. Further factors such as the effect of sensing area reduction and response to random gas concentrations are also tested on AlN-and ScAlN-based pyroelectric detectors respectively to observe the gas sensing behaviors of both detectors. The results obtained provide further understanding of the behavior of CMOS AlN-and ScAlN-based pyroelectric detectors as IR gas sensors, which can potentially inspire new design and design selection for various gas sensing applications.

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Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring

Lai

Liu

Zhou

et al. 2022

Adv Funct Materials

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Non‐dispersive infrared (NDIR) gas monitoring has advantages of environment stability, convenient operation and maintenance, wide detection range, and multi‐gas‐detection capability. However, the conventional IR sources for NDIR gas monitoring, such as miniature lamps, microelectromechanical system (MEMS) light sources, and light‐emitting diodes (LEDs), can only work at narrow modulation frequency and spectral range, or require complicated design and fabrication, because of the constraint of materials and work principle. These issues cause low data acquisition rate, poor anti‐interference ability and limited gas compatibility to NDIR. Here, the super‐aligned carbon nanotube (SACNT) film is developed as an IR source in NDIR gas monitoring system. It has a wide spectral range (0.2–334 µm), a facile fabrication method, and can work up to a high frequency ≈150 kHz. A mechanical‐chopper‐free and wide‐concentration‐range monitoring equipment for CO2 and CH4 greenhouse gases is demonstrated with SACNT film IR source. The concentration ranges for CO2 and CH4 investigated in this paper are 0.0195–20.10% (v/v) and 0.10–17.11% (v/v), respectively. It can be easily applied to monitor other kinds of gases as well.

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A design of an ultra-compact infrared gas sensor for respiratory quotient (qCO2) detection

Cited by 19 publications

References 15 publications

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

CMOS AlN and ScAlN Pyroelectric Detectors with Optical Enhancement for Detection of CO₂ and CH₄ Gases

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring

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A design of an ultra-compact infrared gas sensor for respiratory quotient (qCO2) detection

Cited by 19 publications

References 15 publications

Miniaturized CO2 Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

Miniaturized CO2 Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

CMOS AlN and ScAlN Pyroelectric Detectors with Optical Enhancement for Detection of CO2 and CH4 Gases

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring

Contact Info

Product

Resources

About

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

Miniaturized CO₂ Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector

CMOS AlN and ScAlN Pyroelectric Detectors with Optical Enhancement for Detection of CO₂ and CH₄ Gases