Fabrication by electron beam lithography and preliminary studies by high resolution electron microscopy techniques of perovskite nanostructures
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In order to study thin films of complex oxides deposited on discontinuous surfaces, necessary techniques to fabricate templates and analysis of templates and thin-film samples at atomic scale have been investigated. Sub-micron stripe structures were fabricated by electron beam lithography and Ar-ion etching on 0.5 wt% Nb-doped SrTiO3 substrates. Tripod polishing was applied to make transmission electron microscopy (TEM) samples, which is a very site specific sample preparation method providing high quality TEM samples. Both plane-view and cross-section samples were examined by TEM, confirming the periodicity and stripe width from measurements by atomic force microscopy. Tripod polished and low-angle, low-energy Ar-ion milled under liquid nitrogen cooling cross-section samples of epitaxial PbTiO3/ SrTiO3 thin-films were examined by high resolution TEM, revealing an atomically sharp and defect-free interface. Comparing the experimental micrographs with multi-slice simulations qualitatively gave a good match. A ~10 unit cell thick layer with increased intensity was found, by examining the interface with low angle annular dark field scanning TEM. This layer origins from a polarization gradient near the interface, and confirms the results from previous studies on ion milled samples. The results obtained from thin-film samples can serve as a reference for thin films grown on structured surfaces in the future.