Electrical conduction in (Ba, Sr)TiO3 thin film MIS capacitor under humid conditions

Barium strontium titanate (BST) thin films are made on n-type Si substrate by the sol-gel technique to study electrical conduction in a metal-insulato r-semiconductor (MIS) device under humid conditions. These films are porous and adsorb the water vapour when exposed to a humid environment, Due to ad sorption of the water vapor, a large shift of similar to 1 volt in flat ban d voltage from C-V measurements is observed. An attempt has been made to un derstand the current conduction mechanism in these films under different hu midity conditions. Impedance measurements have been made at various frequen cies and at different humidity levels to distinguish individual contributio ns to electrical conduction, arising from different sources like bulk and g rain boundaries, inter granular contact regions and electrode-sample interf ace regions on the basis of non-Debye theory. We have proposed a physical m odel and its equivalent circuit to explain the skewed semicircles in the Co le-Cole plot of the experimentally acquired data. (C) 2001 Elsevier Science Ltd. All rights reserved.