Electrical conduction mechanism in high-dielectric-constant (Ba0.5,Sr0.5)TiO3 thin films

The electrical conduction mechanism of (Ba-0.5,Sr-0.5)TiO3 (BST) as a function of the temperature was studied. Au/BST/Pt metal-insulator-metal capacitors were fabricated. The temperature range was from 300 to 423 K. The conduction current depended on the voltage polarity. At high electrical field (>800 kV/cm) and with the Pt electrode biased negatively, the Pt/BST interface forms a Schottky barrier with a barrier height of 0.58 eV from 300 to 373 K. The Au/BST interface forms an ohmic contact. The conduction current when the Au electrode is biased negatively shows space-charge-limited-current behavior. An energy band diagram is proposed to explain the experimental results. (C) 2002 American Institute of Physics.