{"database":"biostudies-literature","file_versions":[],"scores":null,"additional":{"submitter":["Ng DKT"],"funding":["Agency for Science, Technology and Research","National Research Foundation Singapore"],"pagination":["2345-2357"],"full_dataset_link":["https://www.ebi.ac.uk/biostudies/studies/S-EPMC9425554"],"repository":["biostudies-literature"],"omics_type":["Unknown"],"volume":["7(8)"],"pubmed_abstract":["NDIR CO<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> gas sensor, we are able to measure the gas response from 5000 ppm down to 100 ppm of CO<sub>2</sub> gas concentration with CO<sub>2</sub> gas response time of ∼5 s, sufficient for practical applications as the average outdoor CO<sub>2</sub> level is ∼400 ppm. The selectivity of this miniaturized CO<sub>2</sub> gas sensor is also tested by mixing CO<sub>2</sub> with nitrogen and 49% sulfur hexafluoride, respectively. The results show high selectivity to CO<sub>2</sub> 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<sub>2</sub> gas sensors based on pyroelectric detectors, which could possibly be integrated with consumer electronics for real-time air quality monitoring."],"journal":["ACS sensors"],"pubmed_title":["Miniaturized CO<sub>2</sub> Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector."],"pmcid":["PMC9425554"],"funding_grant_id":["U2102d2012","A1789a0024"],"pubmed_authors":["Xu L","Fu YH","Lee LYT","Ng DKT","Zhang T","Chen W","Gu Z","Wang H","Chia XX","Zhang Q","Jaafar N","Ho CP"],"additional_accession":[]},"is_claimable":false,"name":"Miniaturized CO<sub>2</sub> Gas Sensor Using 20% ScAlN-Based Pyroelectric Detector.","description":"NDIR CO<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> gas sensor, we are able to measure the gas response from 5000 ppm down to 100 ppm of CO<sub>2</sub> gas concentration with CO<sub>2</sub> gas response time of ∼5 s, sufficient for practical applications as the average outdoor CO<sub>2</sub> level is ∼400 ppm. The selectivity of this miniaturized CO<sub>2</sub> gas sensor is also tested by mixing CO<sub>2</sub> with nitrogen and 49% sulfur hexafluoride, respectively. The results show high selectivity to CO<sub>2</sub> 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<sub>2</sub> gas sensors based on pyroelectric detectors, which could possibly be integrated with consumer electronics for real-time air quality monitoring.","dates":{"release":"2022-01-01T00:00:00Z","publication":"2022 Aug","modification":"2025-04-04T21:52:36.279Z","creation":"2025-04-04T21:52:36.279Z"},"accession":"S-EPMC9425554","cross_references":{"pubmed":["35943904"],"doi":["10.1021/acssensors.2c00980"]}}