Study of hydrogen polarization potential in MFM device using amorphous (Ba, Sr)TiO₃ type thin films and hydrogen gas sensing preporties

Ferroelectric (Ba,Sr)TiO₃ type thin films, with and without Ti and La doping, have been prepared by the sol-gel technology and characterized using TGA, DTA, X-ray diffraction, dielectric characterizations, and gas sensing measurements for H₂ detection. The BST thin film capacitive devices are made on Si substrate to detect H₂ gas and to study the hydrogen induced interfacial polarization potential. Experimental results show that the Schottky I-V behavior exhibits in these Pd/amorphous (Ba,Sr)TiO₃ type thin film/metal capacitive devices, and that the enhanced interfacial polarization potential as large as 4.5 V at 1042 ppm H₂ gas diluted in air has been observed, which is about 7 times larger than the best value reported in the literature. It has been clearly shown that the hydrogen induced interfacial polarization potential is closely correlated with the microstructure in ferroelectric thin films and the enhancement of this polarization potential is mainly attributed to the high dielectric constant of amorphous ferroelectric thin films. A hydrogen-blocking model is proposed to explain this interesting phenomenon. Other factors such as compositions, stoichiometry, processing conditions, are also discussed.