Thin Film Growth Using Hetero Embryo: Demonstration on Pyrochlore Phase

The paper reports the possible use of nanoparticles embedded in amorphous host as hetero embryos in order to grow complex crystalline phases as thin film. Demonstration is performed in the prototypical case of pyrochlore phase Gd(2)Ti(2)O(7) grown from Gd(2)O(3) nanoparticles embedded in TiO(2) matrix at low temperature. As embryos, two kinds of nanoparticles are compared: clusters deposited by low energy cluster beam deposition (LECBD) and nanostructured films elaborated by sol-gel process. The growth has been analyzed by X-ray diffraction and transmission electron microscopy. Furthermore, the nanoparticles have been doped with Eu(3+) luminescence probes in order to follow the nucleation mechanisms at the atomic scale. It is shown that the size, shape, and composition of hetero embryos and as well their interfaces are of paramount importance to enhance the formation of complex materials, such as pyrochlore. By this mean, the first step in classical nucleation science, controlling the height of the energetic barrier, is skipped and the synthesis conditions can be eased.