Study of the electrical properties of pulsed laser ablated (Ba0.5Sr0.5)TiO3 thin films

The laser ablated barium strontium titanate (BST) thin films were character ized in terms of composition, structure, microstructure and electrical prop erties. Films deposited at 300 degrees C under 50 mTorr oxygen pressure and 3 J cm(-2) laser fluence and further annealed at 600 degrees C in flowing oxygen showed a dielectric constant of 467 and a dissipation factor of 0.02 . The room-temperature current-voltage characteristics revealed a space cha rge limited conduction (SCLC) mechanism, though at low fields the effect of the electrodes was predominant. The conduction mechanism was thoroughly-in vestigated in terms of Schottky emission at low fields, and bulk-limited SC LC at high fields. The change over to the bulk-limited conduction process f rom the electrode-limited Schottky emission was, attributed to the process of tunneling through the electrode interface at high fields resulting into the lowering of the electrode contact resistance and consequently giving ri se to a bulk limited conduction process. The predominance of SCLC mechanism in the films suggests that the bulk properties are only revealed if the de pletion width at the electrode interface is thin enough to allow the tunnel ing process to take place. This condition is only favorable if the him thic kness is high or if the doping concentration is high enough. In the present case the film thickness ranged from 0.3 to 0.7 mu m which was suitable to show the transition mentioned above. (C) 1999 Elsevier Science S.A. All rig hts reserved.