Photoyield and x-ray-photoelectron spectroscopic studies of O2-annealing effects on SrBi2Ta2O9 thin films prepared by pulsed laser deposition

Abstract

Electronic properties of various SrBi2Ta2O9 (SBT) thin films were studied by ultraviolet (UV)-ray photoyield spectroscopy (PYS) and x-ray photoelectron spectroscopy (XPS). The UV-PYS studies have shown that O2 annealing increases the Fermi level in the SBT thin film surface which was prepared by pulsed laser deposition (PLD) by about 0.34 eV, while the other SBT thin films deposited by metalorganic decomposition (MOD) have shown almost the same Fermi levels as the O2-annealed PLD-SBT thin film. The XPS studies of those SBT thin films have shown that the PLD-SBT thin film is more susceptible to deoxidization by Ar+ bombardment than MOD-SBT thin films. This implies that the PLD-SBT thin film includes more defective (Bi2O2)2+ layers than MOD-SBT thin films. The O2-annealing effects on the PLD-SBT thin films are thought to oxidize defective (Bi2O2)2+ layers on the PLD-SBT surface and to shift the surface Fermi level towards the center of the band gap.