Fabrication of β–BaB2O4 thin films with (00l) preferred orientation through the chemical solution deposition technique

Abstract

β–BaB2O4 (β-BBO) films with the (00l) preferred orientation were successfully fabricated on Si(100) and fused quartz substrates by the chemical solution deposition technique. The films were characterized by x-ray diffractometry in out-of-plane and in-plane geometry, reciprocal space mapping, transmission electron microscopy, and scanning electron microscopy. The degree of orientation of the films is as high as 95% and the full width at half-maximum (FWHM) of the rocking curve for the films is as low as 2.9°. The films have a mosaic structure. The (00l) planes of some of the crystallites tilt to the substrate and the in-plane orientation of each crystallite is random. The size of each crystallite is 0.5–1.5 μm, and crystallite thickness is equal to the film thickness. The degree of orientation of the films increases and the FWHM of rocking curve for the films decreases with increasing film thickness. The thicker the films are, the larger the crystallite size and the more definite the crystallite boundaries are. These phenomena are thought to be closely related with the increase in internal stress with film thickness. The films irradiated by Nd3+: YAG laser light generated second harmonic wave.