This paper describes the fabrication procedure as well as the sensing properties of new hydrogen sensors using Fe,Os-based thin film. The tilm is deposited by the rf. sputtering technique; its composition is FeaO, TiOr(5 mol%) and MgO(O-12 mol%). The conductance change of the tilm is examined in various test gases. The sensitivity to hydrogen gas is enhanced by treating the lihn in vacuum at 550 "c for 4 h and then in air at 700 "C for 2 h. The sputtered film is identified to be polycrystalline a-Fe,03 based on X-ray diffraction patterns. However, the surface layer is considered to be changed to Fe,O, after heating in vacuum and then to rF%Oa after heating in air. The film is thus a multilayer one with a thin rFeaO, layer on an a-Fe,O, layer. The sensing mechanism is discussed based on measurements of the physical properties of the film, such as the temperature dependence of the sensor conductance, X-ray diffraction pattern, surface morphology, RRS (Rutherford backscattering) spectrum and optical absorption spectrum.
eering from the Uni-1 77, respectively. He is engaged in research on thin-film gas and humidity sensors.
Noriyuki Nishida received B.Eng. and M.Eng. degrees in electrical engineering from Tokyo Denki University, in 1988 and 1990, respectively. He is engaged in research on thin-film gas sensors.