Bias sputter deposited Ni/Al2O3 cermet thin films for gas flow sensors

Thin films of Ni/Al2O3 cermet have been prepared by bias rf sputter deposition. A target composed of small Ni bars attached on Al2O3 plate (dia. 5 cm) was used as a sputter source. The sputtering was carried out in pure Ar gas. The resulted films were ceramic/metal composite consist of crystalline Ni metal gains and amorphous Al2O3 as characterized by X-ray diffraction and transmission electron microscope. Film morphology was observed by scanning electron microscope and was found to vary with applied bias. The films can be heated as a suitable current was applied, and the film resistance changed with film temperature. By measuring the resistance variation under different flow rates, the films can be used as flow sensors. The performances of the films deposited under different conditions were tested and compared.