Strain relaxation by directionally aligned precipitate nanoparticles in the growth of single-crystalline Gd-doped ceria thin films

Transmission electron microscopy has been used to investigate the microstructure and epitaxial behavior of gadolinium-doped ceria (Ce0.8Gd0.2O2-delta) thin films on single crystal (001) LaAlO3. The results show that the films have single-crystal cubic structure and a sharp interface with an interface relationship of (001)(film)parallel to(001)(sub) and [100](film)parallel to[110](sub). Accompanying the high film crystallinity, a directionally aligned, precipitated nanoparticle structure has been observed. The precipitated particles have an average size of similar to4 nm, a Ga-rich composition of Ce0.7Gd0.3O2-delta, a rhombic shape with mainly {111} facets, and are uniformly distributed over the entire film area. The nanoparticles contribute a uniform tensile strain to the film that effectively compensates the compressive film strain induced by the substrate, and also leads to a uniform relaxation of the residual film strain by generating misfit dislocations at the film/particle interfaces. The high film crystallinity is believed to result from this uniform film strain relaxation mechanism. (C) 2004 American Institute of Physics.