Microstructural analyses of a highly conductive Nb-doped SrTiO3 film

The microstructural characteristics of a highly conductive Nb-doped SrTiO3 thin film grown on (0 0 1) SrTiO3 substrate by laser molecular beam epitaxy were extensively studied by means of transmission electron microscopy. It was found that the film was of single-crystal form and epitaxially grown on the SrTiO3 substrate forming a flat and distinct interface. Threading dislocations were hardly found within the film and their absence is believed to be the main contributor to the good electrical properties. The Nb-riched nano-agglomerates, which are homogeneously embedded in the film, were found to induce the diffusion interfaces with their surrounding mediums. Pure edge misfit dislocations with Burgers vectors of a〈0 1 1〉 type and line directions of 〈1 0 0〉 were found to be the major interfacial defects responsible for the misfit relief. Such dislocations were further dissociated into two equal partial dislocations with Burgers vectors of a/2〈0 1 1〉. The high conductivity of the film was discussed from the viewpoint of Nb dopant and the lower oxygen pressure.