Powders and dense thin films of late transition metal oxide nanocomposites from structurally characterized single-source precursorsElectronic supplementary information (ESI) available: further figures and crystallographic details. See http://www.rsc.org/suppdata/jm/b3/b306282a/

Abstract

A new class of heterometallic heteroleptic alkoxides, MII2Ta2(acac)2(OEt)12, MIICo, Ni, has been used as single-source precursors in order to obtain nanophase powders and films. MII2Ta2(acac)2(OEt)12 was prepared via interaction of MII(acac)2, MIICo, Ni, with Ta(OEt)5, in toluene and characterized structurally by single-crystal X-ray diffraction, IR and NMR spectroscopy. Oxide films were deposited by spin coating on Si- and SiO2-substrates. Multiple layers, with intermittent heat treatment, were applied to increase the thickness. After annealing at different temperatures and time, the films were characterized by powder X-ray diffraction and SEM. The films were homogeneous and the thickness could be varied between 0.14 µm and 0.67 µm, depending on solution concentration (0.20–0.28 M) and number of layers (3–6). The nanophase powders were also studied at different annealing temperatures. Powder X-ray diffraction of the films coated on Si-substrate and the nanophase powders revealed the presence of CoTa2O6 and Co3O4 phases for the cobalt-tantalum precursor. NiTa2O6 and NiO phases were detected by powder X-ray diffraction with the nickel-tantalum precursor. Atomic force microscopy revealed the oxide films on the Si-substrate to be very smooth and the root mean square roughness was 2.4 nm for a three-layer oxide film with a thickness of 0.50 µm.