Properties of palladium doped tin oxide thin films for gas sensors grown by PLD method combined with sputtering process

Abstract

The gas sensors based on tin dioxide (SnO 2) thin films and doped with different amount of palladium (Pd) were synthesized by a new developed preparation system using the pulsed Nd:YAG (532 nm) laser deposition method combined with d.c. sputtering. The Pd-doped SnO 2 (SnO 2–Pd) thin films have been grown on Si (1 0 0) and alumina (Al 2O 3) substrates using SnO 2 targets. The composition ratio and the bonding states of SnO 2–Pd thin films were characterized by an X-ray photoelectron spectroscopy. Surface morphology and structure of the films have been obtained by atomic force microscope and glancing-angle X-ray diffraction measurement. The effects of the sputtering discharge power of Pd on the properties of the SnO 2–Pd thin films are discussed. The gas sensing properties of SnO 2–Pd thin films prepared by this new pulsed laser deposition (PLD) method are also investigated over the temperature range 200–600 °C, using 0.31 vol.%H 2 as a test gas. Experimental results suggest that SnO 2–Pd thin films can be prepared using this new PLD method. Atomic concentration ratio of Pd in the SnO 2–Pd film depends on the sputtering discharge power of Pd and varies from 1 to 6%. The maximum sensitivity of SnO 2–Pd thin film gas sensor synthesized by this new PLD method is approximately 3 times higher than that of pure SnO 2 thin film gas sensor grown by the conventional PLD method.