Orientation mechanism during crystallization of apatite-type lanthanum silicate thin films from an amorphous precursor

Control of the crystallization and orientation of apatite-type lanthanum silicate (LSO) plays an important role in designing and improving the LSO synthesis process. The mechanisms that determine the c-axis preferential orientation of LSO thin films synthesized by chemical solution deposition and their correlation with preparation conditions were investigated. Crystallization was found to be initiated preferentially at the surface of the precursor thin films. It was also found that the orientation of LSO thin films was largely governed by the orientations of the LSO nuclei that formed at the surface of the precursor thin films. In addition, the c-axis orientation was influenced by the atmosphere used during crystallization and the Si/La ratio in the precursor thin films. An oxygen atmosphere during annealing and lower Si/La ratios reduced the degree of c-axis orientation.