In situ x-ray and electron scattering studies of oxide molecular beam epitaxial growth

We perform in situ synchrotron x-ray ray diffraction (SXRD)/reflection high energy electron diffraction (RHEED) studies on the growth of complex oxide thin films by molecular beam epitaxy. The unique deposition chamber, located at the Advanced Photon Source, allows the preparation of complex oxide samples with monolayer precision and facilitates the formation of direct correlations between in situ x-ray studies and the more prevalent RHEED investigations. Importantly, because SXRD and RHEED probe different atomic-scale processes during thin film synthesis, their concomitant use enables the extraction of details concerning growth behavior that one cannot determine from either probe alone. We describe the results of such in situ studies on the epitaxial growth of perovskite LaNiO3 on (La0.18Sr0.82)(Al0.59Ta0.41)O-3 (001). We find that during the earliest stages of growth, the RHEED and x-ray signals do not agree with each other, demonstrating that while regular RHEED oscillations may imply high quality growth, the film-substrate interface can undergo significant changes during deposition due to the occurrence of interdiffusion at the growth temperature.