Enhanced electrical properties of Ba0.5Sr0.5TiO3 thin films grown by ultraviolet-assisted pulsed-laser deposition

In this letter, we report enhanced electrical performance of high-dielectric-constant barium strontium titanate (BST) thin films grown by an in situ ultraviolet (UV)-assisted pulsed-laser deposition (UVPLD) technique. In comparison with conventional pulsed-laser deposition (PLD) BST (i.e., films grown under similar conditions but without UV illumination) and films grown by other techniques, the UVPLD-grown films exhibited improved structural and electrical properties. The dielectric constant of 40-nm-thick films deposited at 650 degrees C by PLD and UVPLD were determined to be 172 and 281, respectively. The density of interface states at the flat-band voltage was found to be approximately 5.6 x 10(11) eV(-1) cm(-2) for the UVPLD-grown BST films, which was almost an order of magnitude lower than that obtained for conventional PLD films. The leakage current density of the UVPLD-grown films was approximately 4 x 10(-8) A/cm(2) at 100 kV/cm, which was nearly 1.5 times lower than that obtained from the PLD deposited films. The equivalent silicon dioxide thickness of the best BST films grown was found to be around 10 Angstrom. (C) 1999 American Institute of Physics. [S0003-6951(99)05745-9].