Ferroelectric (Ba, Sr)TiO3 thin films for H2 gas detection by sol-gel and RF sputtering

Abstract

Ferroelectric (Ba, Sr)Ti03 thin films for hydrogen gas detection have been prepared by sol-gel and RF sputtering methods, and characterized using X-ray diffraction, dielectric characterization, and gas sensing measurements. The sol gel approach can easily produce BST amorphous films for H2 gas detection, however, no amorphous films, but partially crystallized ones, have been obtained using our RF sputtering coating system. Experimental results show that the Schottky I-V behavior appears in these Pd/amorphous BST thin fildmetal capacitor devices, both in air and in diluted hydrogen gas. The sol-gel prepared films display an excellent gas sensitivity and the turn-on voltage shift as large as 4.5V at 1024 ppm H2 gas in air has been observed due to the H2 blocking effect by amorphous BST films. The relatively poorer performance of the RF sputtered films to H2 gas detection may originate from the trapped charges in these partially crystallized films, and therefore, weaken the induced H2 potential build-up across the space charge layer at the interface.