Microstructure and hydrogen gas sensitivity of amorphous (Ba,Sr)TiO3 thin film sensors

Ferroelectric (Ba0.67Sr0.33)Ti1.02O3 thin films have been prepared by the s ol-gel technology and characterized using TGA, DTA, XRD, TEM, dielectric ch aracterizations, and gas sensing properties. The (Ba0.67Sr0.33)Ti1.02O3 thi n film devices are made on Pt-coated Si substrate to detect hydrogen gas an d to study gas sensing mechanism. Experimental results show that the diode I-V behavior appears in these Pd/amorphous (Ba,Sr)TiO3 (BST) thin film/meta l capacitive devices, and that the enhanced voltage shift as large as 4.5 V at 1042 ppm hydrogen gas in air has been observed. Compared with the avail able data in the literature, this obtained value of voltage shift in our ex periment is about seven times larger than the best one reported under simil ar testing conditions. It has been clearly shown that the hydrogen-induced voltage shift is closely correlated with the microstructure of ferroelectri c thin films and the enhancement of this polarization potential is mainly a ttributed to the high dielectric constant of amorphous ferroelectric thin f ilms. In this paper, we report our experimental results of this new hydroge n gas sensor and discuss the relationship between microstructure and hydrog en gas sensitivity in these ferroelectric thin film sensors. (C) 2000 Elsev ier Science S.A. All rights reserved.