Optical Properties of Vanadium Pentoxide Deposited by ALD

Nanostructures of V₂O₅ find important technological applications in optics, catalysis, and lithium ion batteries. Their optical properties and surface roughness are important parameters in these respects. Here we report on atomic layer deposition (ALD) of V₂O₅ using the β-diketonate VO­(thd)₂ and ozone as precursors. In this work, X-ray diffraction, AFM, ellipsometry, and UV–vis-spectroscopy are used to show that the crystallographic orientation, optical properties, band gap, and surface roughness of the derived films are correlated and can be varied by controlling deposition temperature and film thickness. The band gap of the samples varies between 2.70 and 2.35 eV. The observed growth rate varies between 0.1 to 1 Å/cycle depending on deposition temperature and the number of cycles. This large variation in growth rate provides an interesting case of ALD growth, which can be rationalized in terms of a geometric crystal growth model

Phase Control in Thin Films of Layered Cuprates

Perovskite-related layered cuprates are considered the basis of all high-<i>T</i>_c superconductors. Considerable effort has been put into understanding these materials. Deposition of phase-pure and oriented thin films can help shed light on the unusual interplay between the structure and properties, as the copper layers will be oriented in the same direction throughout the sample. Chemical deposition routes have been considered difficult, because of detrimental decomposition of metalorganic precursors, catalyzed by deposited copper species. In the current paper, we present a route for atomic layer deposition (ALD) of layered lanthanum cuprates. The system exhibits remarkable stoichiometric control, enabling deposition of a variety of lanthanum cuprate species. La₂CuO₄ films is shown to be tetragonal and (001) oriented on LaAlO₃ (100)_pc, with the copper planes parallel to the film surface. We go on to demonstrate that the oxygen-stoichiometry of LaCuO_3–<i>x</i> films can be tuned by post-treatment, resulting in phase control of the complex perovskite lanthanum cuprate system. Epitaxial films have been obtained for oxygen annealed monoclinic and air annealed orthorhombic variants of LaCuO_3–<i>x</i> on LaAlO₃ (100)_pc substrates with a LaCuO_3–<i>x</i>(100)|[640]||LaAlO₃(100)_pc|[310]_pc and LaCuO_3–<i>x</i>(100)_pc|[110]_pc||LaAlO₃(100)_pc|[110]_pc epitaxial relationship, respectively

Atomic Layer Deposition of Spinel Lithium Manganese Oxide by Film-Body-Controlled Lithium Incorporation for Thin-Film Lithium-Ion Batteries

Lithium manganese oxide spinels are promising candidate materials for thin-film lithium-ion batteries owing to their high voltage, high specific capacity for storage of electrochemical energy, and minimal structural changes during battery operation. Atomic layer deposition (ALD) offers many benefits for preparing all-solid-state thin-film batteries, including excellent conformity and thickness control of the films. Yet, the number of available lithium-containing electrode materials obtained by ALD is limited. In this article, we demonstrate the ALD of lithium manganese oxide, Li_<i>x</i>Mn₂O₄, from Mn­(thd)₃, Li­(thd), and ozone. Films were polycrystalline in their as-deposited state and contained less than 0.5 at. % impurities. The chemical reactions between the lithium precursor and the film were found not to be purely surface-limited but to include a bulk component as well, contrary to what is usually found for ALD processes. In addition, we show a process for using Li­(thd)/ozone and LiO^<i>t</i>Bu/water treatments to transform ALD-MnO₂ and ALD-V₂O₅ into Li_<i>x</i>Mn₂O₄ and Li_<i>x</i>V₂O₅, respectively. The formed Li_<i>x</i>Mn₂O₄ films were characterized electrochemically and found to show high electrochemical capacities and high cycling stabilities