Development of High Selective and High Sensitive Air Gas Sensor for Environmental Protection by PLD Method

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In this research, the gas sensors based on tin dioxide (SnO_2) and tungsten oxide (WO_3) thin films doped with different amount of palladium (Pd) and gold (Au) were deposited by the PLD method. The PLD method has become a widely used technique for the deposition of thin films during the past few years due to the advantages of a simple setup, wide ranging deposition conditions, wider choice of materials and higher instantaneous deposition rates. The following conclusions can be drawn from the results.1)We have successfully deposited SnO_2 and WO_3 thin films by the pulsed Nd:YAG (532nm) and pulsed KrF excimer (248nm) laser deposition methods. The surface morphology of the films was observed by a field-emission scanning microscope (FE-SEM) and an atomic force microscope (AFM). The crystalline structure and crystallographic orientation were characterized by GXRD and the composition of the films was measured by X-ray photbelectron spectroscopy (XPS).2)We have successfully prepared H_2 sens … More itive SnO_2-Pd thin films using the new PLD method combined with d.c. sputtering. The films have a polycrystalline structure which is suitable for gas sensing. The Pd atomic concentration of the SnO_2-Pd film depends on the Pd sputtering discharge power. The gas sensitivity of the SnO_2-Pd film prepared using new.PLD method was increased with the sputtering discharge power of Pd.3)We have synthesized NOx sensitive WO_3-Au and WO_3-Pd thin films using new PLD method. The gas sensitivity of the WO_3-Au thin film prepared using new PLD method for 200ppm NO_2 gas was increased with the sputtering power of Au at the range of 3.5 -5 W.4)We prepared CrC, TiC, CN, cBN, TaN films as a hard material and TiO_2 films as a photocatalyst by PLD method. These processes were compared with the SnO_2 and WO_3 thin film gas sensor preparation process.Our experiments show that our new PLD process is simple and effective technique to fabricate high-quality thin film gas sensors. It might be very important to study PLD process scientifically and industrially. Less