WO3-based Hydrogen Gas Sensors Using Stacked Thin Films with Interspace

Hydrogen gas sensors using stacked WO
₃
-based films with interspace has been demonstrated. In order to enhance hydrogen sensitivity and selectivity, porous WO
₃
+TiO
₂
sensing films are deposited and stacked by RF sputtering and thermal treatment. Additionally, interspaces between the sensing films were fabricated by sacrificial layer etching of SiO
₂
, which allowed hydrogen molecules to adsorb on all WO
₃
+TiO
₂
surfaces. Without using any noble metal catalysts, a four-stacked WO
₃
+TiO
₂
hydrogen sensor was highly sensitive to hydrogen ranging from 10 ppm to 3000 ppm. The response and recovery times of the sensor to hydrogen of 1000 ppm were 35 s and 30 s, respectively. Moreover, the stacked structure with interspace suppressed the response of the sensor to various combustible gases, such as isobutane, methane, ethylene, and propane. Because the sensitivity of the sensor was more stable after an aging process, the proposed sensor is suitable for a continuous and long-term monitoring of a hydrogen gas leakage.