Heteroepitaxial growth of transition metal oxides using UHV laser molecular beam epitaxy

Abstract

We have grown heteroepitaxial thin film structures composed of various transition metal oxides such as the colossal magnetoresistance manganites, superconducting cuprates, ruthenates as well as insulating titanates on SrTiO<SUB>3</SUB>, NdGaO<SUB>3</SUB> and LaAlO<SUB>3</SUB> substrates using a UHV laser molecular beam epitaxy (laser-MBE) system. The film growth was controlled in-situ using high pressure RHEED as well as scanning probe techniques (AFM/STM). The fabricated films were analyzed by x-ray diffraction, transmission electron microscopy and the measurement of the transport properties. The manganite, ruthenate and titanate thin film structures show good epitaxy with small mosaic spread. The observation of RHEED oscillations during the film deposition indicates a layer by layer growth mode. This is further supported by the observed small surface roughness of typically less than 3 nm rms for a 100 nm thick film. We also could find a clear correlation between the observed RHEED pattern and the surface morphology measured by AFM/STM. Our analysis shows that UHV laser MBE is well suited for the fabrication of complicated heteroepitaxial thin film structures required for oxide electronics.