Pd Thin Films on Flexible Substrate for Hydrogen Sensor

Abstract

In this work, palladium (Pd) thin films were prepared via RF sputtering method with various thicknesses (6 nm, 20 nm and 60 nm) on both a flexible substrate and a hard substrate. Hydrogen (H2) sensing properties of Pd films on flexible subtrate have been investigated depending on temperatures (25 – 100 ºC) and H2 concentrations (600ppm- 10%). The effect of H2 on structural properties of the films was also studied. The films were characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction. It is found that whole Pd films on hard substrate show permanent structural deformation after exposed to 10% H2. For 30 minutes. But, this H2 exposure does not causes any structural deformation for 6nm Pd film on flexible substrate and 6nm Pd film on flexible substrate shows reversible sensor response up to 10% H2 concentration without any structural deformation. On the other hand, Pd film sensors that have the thicknesses 20 nm and 60 nm on flexible subtrate are irreversible for higher H2 concentration (>2%) with film deformation. The sensor response of 6 nm Pd film on flexible subtrate increased with increasing H2 concentration up 4% and then saturated. The sensitivity of the film decreased with increasing operation temperature.