Influence of oxygen pressure on the lattice constants of Ba0.6Sr0.4TiO3 thin films and preparation of BaTiO3/Ba0.6Sr0.4TiO3 superlattices

Abstract

Using pulsed laser deposition (PLD) technology, BaTiO3 (BT) and Ba0.6Sr0.4TiO3 (BST) single-layer films were successfully prepared through a series of optimization experiments. X-ray diffraction investigations indicated that BT and BST thin films were nearly (001)-epitaxially grown on LaAlO3 (001) substrates. And functional relation between the lattice constants of BST thin films and the oxygen pressure was close to Boltzmann function from 10-3 to 25 Pa. Then the high-quality BT/BST superlattices were also prepared under these optimal conditions. The surface topography measurement by atomic force microscopy (AFM) demonstrated that the root-mean-square (RMS) roughness of BT/BST superlattice was only 0.3048 nm. The surface smoothness has achieved the atomic scale. In addition, satellite peaks were clearly observed in the XRD spectrum. According to the position of satellite peaks that belong to (002) diffraction peak, the superperiod of superlattices was calculated and the deposition rates of BT and BST thin films were deduced. Finally, laser induced thermoelectric voltage (LITV) effect was measured for the first time in BT/BST superlattices grown on vicinal-cut single crystal substrates, which was not found in BT and BST single-layer films.