Fabrication by electron beam lithography and preliminary studies by high resolution electron microscopy techniques of perovskite nanostructures

Abstract

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.