Design and fabrication of micro carbon dioxide sensor based on TiO₂ thin film

Abstract A micro-electro-mechanical systems (MEMS)-based micro carbon dioxide sensor is fabricated using conventional photolithography, electron beam evaporation, and radio frequency sputtering techniques. The sensor consists of a titanium dioxide sensing layer, interdigital electrodes (IDEs), a platinum resistance temperature detector (RTD), and an aluminium oxide substrate. Given a working temperature greater than 300°C, the resistance of the titanium dioxide sensing layer increases linearly with an increasing carbon dioxide concentration. Fluctuations in the working temperature are detected by the RTD and compensated using a proportional-integral-derivative (PID) feedback control system implemented in LabVIEW. The temperature detection results reveal that the RTD has a sensitivity of 1.3 mV/°C. The sensor is calibrated using a standard carbon dioxide detector and is used to perform carbon dioxide sensing at working temperatures of 300°C, 350°C, and 400°C, respectively. It is shown that the highest sensitivity of (0.179 MΩ/ppm) and fastest response time (15 seconds) are attained at a working temperature of 350°C.