WO3-Pd Structure in SAW Sensor for Hydrogen Detection

In the paper a new sensor structure for surface acoustic wave gas system is presented.A bilayer structure WO 3 -Pd thin films may be useful for hydrogen detection in low concentration in air.A bilayer sensor structure of tungsten oxide WO 3 with a very thin catalytic film of palladium on the top has been studied for gas-sensing application at room temperature (about 25 • C) in surface acoustic wave system.The bilayer structure of WO 3 layers with a thickness of about 50 nm, 100 nm and 150 nm was made onto a LiNbO 3 Y -cut Z-propagating substrate by means of the vacuum sublimation method using a special aluminum mask.The vapor source consisted of commercially available WO3 powder (Fluka 99.9%) and molybdenum heater.The thin palladium (Pd) layer (about 10 nm) was made separately on each WO3 layer by means of vapor deposition in high vacuum.There have been investigated three structures: 50 nm WO3 + 10 nm Pd, 100 nm WO3 + 10 nm Pd and 150 nm WO3 + 10 nm Pd in three canal surface acoustic wave system with reference oscillator.Numerical results obtained by analysis of the surface acoustic wave gas sensor model have been compared with experimental results.