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

Abstract.

The microstructure and properties of barium strontium titanate (BST) thin films grown by an in situ ultraviolet-assisted (UV-assisted) pulsed laser deposition (UVPLD) technique are reported in this paper. In comparison with BST films grown by conventional pulsed laser deposition (PLD) under similar conditions, but without UV illumination, the UVPLD-grown films exhibited improved structural, electrical, and optical properties. X-ray photoelectron spectroscopy showed that when exposed to atmosphere, Ba atoms from the outermost layers formed a thin layer of barium carbonate, which negatively affects the film electrical characteristics. UVPLD-grown films exhibited a smaller amount of Ba atoms within the carbonate layer, resulting in better electrical characteristics. The dielectric constant of 40-nm-thick films deposited at 650 °C by UVPLD and PLD were determined to be 281 and 172, respectively. The leakage current density of the UVPLD-grown films was in the mid-10^-8 A/cm² range, a factor of 2 lower than that obtained from PLD-grown films.