Defect structure of heteroepitaxial SnO2 thin films grown on TiO2 substrates

Heteroepitaxial SnO2 thin films were grown on rutile (100) TiO2 single crystal substrates by pulsed laser deposition. The defect structure and surface morphology were investigated by transmission electron microscopy, reflection high-energy electron diffraction, and atomic force microscopy. The misfit-induced large biaxial compressive stress in the 200-nm-thick SnO2 thin film was almost fully relaxed to yield the high-density interfacial misfit dislocations and related planar defects. The misfit dislocation network on the hetero-interface consisted of two types of partial edge dislocations with Burgers vectors of 1/2 and 1/2, which involved {101} and {010} planar defects formed in the film, respectively. The evolution of the surface morphology and cross-sectional structure for thinner films suggested that the introduction of such defects occurs at the early growth stage, due to large lattice misfit, and is strongly affected by point defect condensation.