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Abstract: This work is devoted to deposition of alumina–silica films using an innovative pulsed injection metal organic chemical vapour deposition technique and aluminium tri(iso-propoxide) (Al(i-OPr)3) and tetraethoxysilane (TEOS) as precursors. The deposited aluminium silicate films have been characterised by scanning electron microscopy, infrared spectroscopy, X-ray diffractometry and capacitance–voltage (C–V) measurements. The investigation of the deposition at different Si/Al ratios and substrate temperatures has shown that the growth rate increases with the increase of Al(i-OPr)3 proportion in solution and decreases as the proportion of TEOS increases. We have also shown that aluminium content in the film increases at lower deposition temperatures while silicon content increases at higher temperatures. The permittivity of the films determined from C–V measurements decreases with increasing substrate temperature. It was found that films deposited at substrate temperatures of 600 or 700 °C and with the highest Si/Al ratio have the lowest dielectric permittivity. This research should be useful for further development of MOCVD technology for the deposition of aluminosilicate-based dielectric materials with controlled dielectric permittivity. [Copyright &y& Elsevier]

Dense ceramic mixed ionic and electronic conducting membranes have been deposited by atmospheric spray-pyrolysis technique onto porous ceramic substrates. Perovskite oxide layers, i.e. manganites La1-xSrxMnO3, ferrites La1-xSrxFe1-y(Co,Ni)yO3, gallates La1-xSrxGa1-y(Co,Ni,Fe)yO3, cobaltites La1-xSrxCoO3 and related perovskites such as lanthanum nickelate La2NiO4 layers have been prepared. The structure, morphology and composition of the layers were characterised by XRD, SEM and WDS, respectively. Density and gas tightness of the layers were studied as a function of deposition process parameters, film thickness (from ∼0.5 to ∼3 μm) and preparation procedure. The presence of cracks and defects due to thermo-mechanical stresses applied during or after the preparation process were correlated with the membrane composition and the corresponding thermal expansion coefficient differences between substrates and membranes. [Copyright &y& Elsevier]

We report on large external magnetic field effects during pulsed injection metal-organic chemical vapor deposition of magnetite films on MgO(001). The application of a 1 T field during the growth process significantly increases the saturation magnetization of magnetite by 150%–220% at a deposition temperature of 550 and 600 °C, while the enhancement of the remanent magnetization is even larger. This anomalous magnetic field effect does not drastically alter the crystalline texture, surface morphology, and film thickness of magnetite, but is explained by a suppression of antiphase-boundary formation during film growth. [ABSTRACT FROM AUTHOR]

We report on large magnetic moments of up to 18.9μB/Co in Co-doped ZnO films grown by pulse-injection metal organic chemical vapor deposition. The magnetic moment saturates easily in perpendicular magnetic fields and is considerably reduced when the magnetic field is applied parallel to the film plane. The saturation moment is largest for a small Co doping concentration of 1% and persists up to a temperature well above 900 K. These extraordinary magnetic attributes cannot be explained by the spin-only moment of Co2+ ions or Co cluster, but suggest the formation of orbital states in a defect-related impurity band. [ABSTRACT FROM AUTHOR]

This report is on the growth of Fe3O4 nanofilms on Al2O3(0001) and MgO(001) substrates with and without the presence of an external magnetic field using a pulsed injection metallorganic chemical vapour deposition (PI MOCVD) technique. The effects of growing magnetic oxide nanofilms in a 1 T field have been examined using various instrumental methods. It was found that the application of a magnetic field during PI MOCVD does not drastically alter the crystalline texture, surface morphology, and film thickness, but it significantly modifies the Fe3O4 film magnetisation and coercive field. Moreover, it was shown that the application of a 1 T field during the cooling of the sample also improves the magnetic properties. We believe that the large external field orients the magnetic spin structure at high temperatures (during growth or the initial stages of cool down) and that cooling through local magnetic ordering temperatures at Fe3O4 defect sites subsequently favours a ferromagnetic spin alignment. The control of magnetic properties of magnetite nanofilms by the application of magnetic fields during growth opens up new routes towards the fabrication and application of magnetic thin film devices. [ABSTRACT FROM AUTHOR]

Abstract: We report on pulse-injection metal organic chemical vapor deposition (PI-MOCVD) and characterization of films on (1102) sapphire substrates. The use of Zn(tmhd)2 and Co(tmhd)3 precursors produces high-quality films in which Co ions replace Zn2+ without disrupting the ZnO lattice. The films are magnetic at room temperature for and the magnetic moments are particularly large for small Co doping concentrations ( for and for ). These large moments and the decrease of the saturation moment with increasing Co content cannot be explained by the formation of Co clusters. We instead believe that the magnetic behavior of the PI-MOCVD grown samples is an intrinsic property of the films. [Copyright &y& Elsevier]

Perovskite oxide layers, i.e. manganites La1−x(Sr,Ca)xMnO3, ferrates La1−xSrxFe1−yCoyO3, gallates La1−xSrxGa1−y(Co,Ni,Fe)yO3 of a thickness of 0.8–2 μm, were deposited by pulsed injection MOCVD (metal-organic chemical vapour deposition) on various monocrystalline and porous ceramic substrates. The layers were characterised by X-ray diffraction, scanning electron microscopy, wavelength dispersion spectroscopy and by electrical measurements of the total conductivity vs. temperature. Such oxides are known as mixed electronic–ionic conductors and are largely studied as materials for the fabrication of oxygen permeable membranes. One of the aims of this work was to estimate the suitability of the pulsed injection MOCVD technique for the preparation of dense perovskite layers for their use as membranes for oxygen. [Copyright &y& Elsevier]

Biaxially textured buffer layers and YBa2Cu3O7 (YBCO) films were grown on NiO/Ni based substrates by pulsed injection MOCVD. High quality biaxially textured NiO layers have been prepared following an optimised recrystallisation–oxidation process. The yttria stabilized zirconia (YSZ) and its combination with CeO2 and/or Y2O3 were investigated in the role of buffer layers for YBCO. Thin biaxially textured buffer layers were deposited in a temperature range from 600 to 800 °C. The best superconducting properties correspond to the Ni/NiO/YSZ/Y2O3/YBCO architecture: YBCO layers were grown epitaxially and exhibited a critical temperature Tc∼90 K (ΔTc⩽1 K) and critical current densities Jc⩾5×105 A/cm2 at 77 K. [Copyright &y& Elsevier]

High quality epitaxial La1−xSrxMnO3 films were deposited by pulsed injection metal organic chemical vapor deposition, using as precursor materials metal-2,2,6,6-tetramethyl-3,5-heptandionates dissolved in monoglyme. The influence of various deposition conditions, substrate material and film thickness on film properties was investigated. The best films were deposited on LaAlO3 substrates at 825 °C: films exhibited a sharp semiconductor–metal transition and high magnetoresistance (∼40%) at a close-to-room temperature and in a rather low field of 1.5 T. In-situ or ex-situ high-temperature annealing in oxygen increased the temperature of semiconductor–metal transition, but decreased the magnetoresistance and the temperature coefficient of resistance. Biaxial strain imposed by the lattices’ mismatch was clearly observed in thinner La1−xSrxMnO3 films on perovskite substrates. Tensile strain was present in the films on SrTiO3 and compressive strain in the films on LaAlO3 (and less clearly on NdGaO3). Both tensile and compressive strains decreased the temperature of electric transition and the values of magnetoresistance. The strain was completely relaxed in the films more than ∼100 nm thick. [Copyright &y& Elsevier]