A new multi-function thin-film microsensor based on Ba_1-xLa_xTiO₃

A new multi-function microsensor with a barium lanthanum titanate (Ba_1-xLa_xTiO₃) thin film is developed for the fabrication of a thin-film resistor and a metal-insulator-semiconductor (MIS) capacitor on a SiO₂/Si substrate. The results reveal that the thin-film resistor has good sensitivity to visible light and good thermal sensitivity within the temperature range of 28-400 °C. The MIS capacitor is sensitive to changes in the relative humidity (RH), with a 130% change of the current for a humidity change from 12 to 92% RH at a test frequency of 500 Hz, and with short response times of 5 and 4.5 s for the adsorption and desorption of water vapor, respectively. The effects of the test frequency on the photo, thermal and humidity sensitivity performances are also investigated. Since the lifetime of charge carriers of Ba_1-xLa_xTiO₃ thin films is only 16 ms, about half that of Sr_1-xLa_xTiO₃ thin films, the device can detect light modulation at higher frequencies.