Fabrication of YBCO/CeO2/YBCO multilayer films through an all chemical solution deposition approach

In this paper, the growth characteristics and superconducting properties of YBCO/CeO₂/YBCO multilayer films derived from an all chemical solution deposition process layer by layer are investigated. X-ray diffraction results show that the c-axis epitaxial growth feature of the bottom YBa₂Cu₃O_7-δ (YBCO) film was perfectly inherited. Alternating epitaxial growth of YBCO/CeO₂/YBCO multilayer films was confirmed by high resolution transmission electron microscopy in combination with selected area electron diffraction, which will lay the groundwork for preparation of SIS-type Josephson junctions. In addition, nanosized BaCeO₃ particle rather than BaCeO₃ transition layer was observed in the interface between YBCO and CeO₂. The superconductivity measurement results show that the proposal method gives better superconducting properties only for high magnetic field and at low magnetic field it deteriorates the superconducting properties.     

Ti-Si-N films prepared by plasma-enhanced chemical vapor deposition

Ti-Si-N thin films were deposited on HSS substrates at 560°C using plasmaenhanced chemical vapor deposition. Feed gases used were TiCl₄, SiCl₄, N₂, and H₂. The composition of the films could be controlled well through adjustment of the mixing ratio of the chlorides in the feed gases. The Si content in the film varied in the range of O to 40 at. %. It was jbund that a small addition of Si to a TiN film improved the morphology significantlv, showing dense and glasslike structure. Also a much smootherand more homogeneous interface between thefilm and the substrate was obtained. The Ti-Si- N films containing 10–15 at. % Si showed the maximal microhardness value of about 6350 kgf/mm², much higher than that of TiN films.     

Preparation and characterization of CuAlO2 transparent thin films prepared by chemical solution deposition method

CuAlO₂ thin films were prepared on quartz glass and sapphire substrates by chemical solution deposition method using copper acetate monohydrate, aluminum nitrate nonahydrate and 2-methoxyethanol as starting precursor and solvent. The effects of annealing temperature on the structural, morphological, electrical and optical properties have been studied. Via the optimized annealing treatment condition, CuAlO₂ film annealed at 850 °C in nitrogen flow of 400sccm under atmosphere pressure exhibits the best performance with the lowest room temperature resistivity of 3.6 × 10² Ω cm and the highest optical transmission in the visible region (>70% at around 600 nm wavelength). CuAl₂O₄ and CuO phases, not CuAlO₂ phase are obtained when annealing temperature is lower than 850 °C. However, a further increase of annealing temperature weakens the crystallization quality and deteriorates the surface morphology of CuAlO₂ films as the annealing temperature exceeds 850 °C, leading to an increase in the resistivity and a decrease of the optical transmission in the visible region of CuAlO₂ films.     

Oriented SrFe12O19 thin films prepared by chemical solution deposition

Thin films of SrFe₁₂O₁₉ (SrM) were prepared from a solution of iron and strontium alkoxides through the chemical solution deposition method on both amorphous (glassy SiO₂), and single crystal substrates (Si(100), Si(111), Ag(111), Al₂O₃(001), MgO(111), MgAl₂O₄(111), SrTiO₃(111)) substrates. The process of crystallization was investigated by means of powder diffraction, atomic force microscopy and scanning electron microscopy. Magnetization measurements, ferromagnetic and nuclear magnetic resonance were used for evaluation of anisotropy in the films. Whilst amorphous substrates enabled growth of randomly oriented SrM phase, use of single crystal substrates resulted in samples with different degree of oriented growth. The most pronounced oriented growth was observed on SrTiO₃(111). A detailed inspection revealed that growth of SrM phase starts through the breakup of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. A continuous film with epitaxial relations to the substrate was produced by repeating recoating and annealing.     

Highly ordered metal oxide nanopatterns prepared by template-assisted chemical solution deposition

TiO₂, Al₂O₃, and ZrO₂ patterns composed of ordered nano motifs of various morphologies (i.e. perforations (craters), rings, canyons, wires, dots, or channels) with typical lateral dimensions of less than 40 nm and thickness below 15 nm are presented. Simple chemical solution deposition (CSD) of molecular inorganic precursors and commercial block copolymers was used to create patterns on several substrate surfaces (bare, hydrophobized or gold covered silicon wafers and ITO). Self-assembly during evaporation and subsequent stabilization at 500 °C leads to the various nanostructures. Compared to other techniques for surface nano patterning, the present method has the advantage of being cheap, reproducible and easy to scale up and does not require specialized equipment. The type, dimension, and organization of these motifs were assessed by AFM, FE-SEM, spectroscopic ellipsometry, and GI-SAXS and are shown to depend on the conditions of preparation. Usage as model surfaces for modelling of wetting properties and as nanoelectrode arrays were investigated.     

Evolution of crystalline structure in SnS thin films prepared by chemical deposition

Crystal structure and morphology undergo significant evolution in thin films of tin(II) sulfide prepared by chemical deposition, over a narrow interval of bath temperature of 20–40 °C, but has not been recognized in previous studies. The chemical bath is constituted using tin(II) chloride, triethanolamine, ammonia(aq.) and thioacetamide. At bath temperature of 20 °C, the deposition rate of the film is 10 nm/h; and at 24 h, a film of thickness 260 nm is obtained. This film is compact and with a predominantly cubic (Cub-) crystalline structure. At 40 °C, the deposition rate is 25 nm/h, and a film of 600 nm in thickness is deposited in 24 h. However, this film has evolved into vertically stacked platelets of orthorhombic (OR-) crystalline structure. The transition from compact-to-platelet morphology as well as from Cub-to-OR-crystalline structure is observed near a deposition temperature, 35 °C. The Cub-SnS has a characteristic high optical band gap, 1.67 eV (direct gap; forbidden transitions) with an electrical conductivity, 10⁻⁷(Ω cm)⁻¹; both properties being un-affected when films are heated at 300 °C in a nitrogen ambient. In OR-SnS, the band gap is 1.1 eV (indirect gap; allowed transitions). The electrical conductivity of such films is notably higher, 10⁻⁴ (Ω cm)⁻¹, which increases further by an order of magnitude when the films have been heated at 300 °C in nitrogen.     

Thick Fe2O3, Fe3O4 films prepared by the chemical solution deposition method

Fe₂O₃, Fe₃O₄ films have been prepared from Fe(OCH₂CH(CH₃)₂)₃–(CH₃)₂CHCH₂OH–2.2′-diethanola- mine (DEA)–poly(vinylpyrrolidone) (PVP) solutions by the spin-(SC) and dip-coating (DC) technique on SiO₂ and Si substrates. The maximum film thickness achieved without crack formation has been increased by incorporation of PVP (relative molecular weights 40000 and 360000) into the precursor solution. The stability of the precursor solutions was remarkably increased by addition of DEA. Compact, dense, and crack-free Fe₂O₃ films with thicknesses 900 nm (DC), 450 nm (SC), have been obtained via single-step deposition cycle. Higher-molecular-weight PVP has been more effective in increasing the thickness. The minimum concentration of DEA, which results in pronounced increase of solutions stability, is about R _P (n(DEA)/n(Fe) = 0.1). The high content of carboneous residue in the pyrolysed Fe₂O₃ films promotes the formation of Fe₃O₄ films via reduction in a gas flow of H₂/N₂ gas mixture. Microstructure, surface morphology, and magnetic properties of the films have been also investigated using SEM, AFM, and SQUID, respectively.     

Tin colloids and metal-metal oxide films prepared by chemical liquid deposition. III

Colloids and thin metal-metal oxide films have been prepared by a method we call Chemical Liquid Deposition (CLD). The metal is evaporated to yield atoms which are solvated at liquid nitrogen temperature, and upon warming stable liquid colloidal solutions are formed. In the case of tin, the particle size of these colloids ranges between 200–500 Å. Zeta potentials were calculated by a Hückel approximation for most of these negatively charged particles. Upon solvent removal, colloidal particles coalesce to form films, which contain some residual solvent. The synthesis of colloids and films from Sn with acetone, 2-butanone, THF, ethanol, 2-propanol, DMF and DMSO is reported. FTIR, High Resolution Mass Spectrometry, Thermogravimetric Analyses (TGA) and Scanning Electron Microscopy (SEM) film characterization has been carried out. These studies indicate that solvents are incorporated into the films. The resistivity studies showed that they more behave as semiconductors than pure metals. TGA studies reveal that loss of weight occurs within 200–500°C. The films are very stable with 5–10% weight loss at 550°C. SEM reveals their surface morphology. Mössbauer gives information about oxidation states of some tin films.     

Epitaxial ternary nitride thin films prepared by a chemical solution method

It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.     

Crystalline orientation of the InN films prepared by atmospheric pressure halide chemical vapor deposition

The structural analysis of the hexagonal InN film prepared on a Si(100) substrate by the AP-HCVD technique using InCl₃ and NH₃ as starting materials were carried out by the X-ray pole figure analysis. The deposited films consist of the hexagonal InN pillar crystals. It was found that the pillar crystals, which have random rotation around the 100 axis, were grown at an angle of 70–90° to the substrate.     

Preparation of nanocrystalline titania films with different porosity by water-based chemical solution deposition

This study describes the synthesis of nanocrystalline titania layers on silicon and glass substrates by chemical solution deposition, using a water-based citratoperoxo-Ti(IV) precursor solution. The same aqueous solution–gel precursor is used for deposition of, both, thin dense layers by spin-coating and thicker porous layers by tape-casting. In the latter, the precursor solution is modified by the addition of polyvinyl alcohol (PVA), which acts as a thickener and pore-forming agent. Phase composition, film morphology, and the hydrophilic character of the films are studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–VIS transmission measurements, variable angle spectroscopic ellipsometry (VASE), and by contact angle measurements. The thin 180 nm titania film, deposited from the unmodified precursor solution, shows a density of about 96%. Upon ultraviolet illumination, it acquires a highly hydrophilic surface. One hour of illumination is sufficient to obtain a water contact angle of almost 0°. Furthermore, the hydrophilisation process shows to be reversible. Tape-casting and thermal treatment of the modified precursor solution gives rise to the formation of a 500 nm thick, porous, pure anatase film. The nanocrystalline thick film is composed of 20–40 nm particles, and contains clearly defined pores of 20 nm, homogeneously distributed along the surface.     

Characterization of zinc-modified lithium tantalate thin films fabricated by chemical solution deposition method

Zinc-substituted lithium tantalate thin films were fabricated for improving the electrical resistivity by compensating the valence of lattice defects in LiTaO₃ crystal. The films with the chemical composition of (Li_1.00-x Zn _x )TaO₃ were fabricated on (111)Pt/TiO₂/SiO₂/(100)Si substrate by a chemical solution deposition technique using metal-organic precursors. Dense films consisting of a ilumenite-type crystalline phase were deposited by spin coating on the substrates, followed by heat-treatment at 650°C for 5 min in air. The leakage current density of the LiTaO₃ film was reduced from approximately 10⁻⁴ to 10⁻⁶ A/cm² by substituting Zn²⁺ ions for Li⁺ ions in the LiTaO₃ films. Polarization–electric field hysteresis loop was improved significantly by partial substitution of Zn²⁺ for Li⁺ ions, which is based on the enhancement of electrical resistivity.     

The use of cationic surfactants to control the structure of zinc oxide films prepared by chemical vapour deposition

This paper describes a powerful and versatile new method for controlling the structure of zinc oxide thin films prepared by aerosol assisted chemical vapour deposition, based on the use of a common surfactant. The technique combines the benefits of solution and vapour based methods and leads to high quality morphologically-defined and orientated thin films.     

Electrochemical deposition and characterization of mixed-valent rhenium oxide films prepared from a perrhenate solution

Cathodic electrodeposition of mixed-valent rhenium oxides at indium tin oxide, gold, rhenium, and glassy carbon electrodes from acidic perrhenate solutions (pH = 1.5 +/- 0.1) prepared from hydrogen peroxide and zerovalent rhenium metal is described. Cyclic voltammetry, variable angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), UV-vis spectroelectrochemistry, and electrochemical quartz crystal microbalance (EQCM) data indicate that the chemical nature of the electrodeposited rhenium species depends mainly upon the potential and supporting electrolyte. The presence of SO4(2-) as a supporting electrolyte inhibits the adsorption of perrhenate, ReO4-, at non-hydrogen adsorbing electrode materials. However, in acidic perrhenate solutions containing only protons and ReO4- anions, strong adsorption of ReO4- at potentials preceding hydrogen evolution occurs. This leads to the formation of an unstable ReIII2O3 intermediate which catalytically disproportionates to form mixed-valent rhenium films consisting of 72% ReIVO2 and 28% Re0. During the hydrogen evolution reaction (HER), hydrogen polarization causes the principle deposit to be more reduced, consisting of roughly 64% ReIVO2 and 36% Re0. Conclusively, metallic rhenium can be deposited at potentials preceding the HER at non-hydrogen adsorbing electrode materials, especially in the absence of SO4(2-) anions.     

Comparative non-isothermal kinetic analysis of thermal degradation of poly(vinyl chloride) prepared by living and conventional free radical polymerization methods

Non-isothermal kinetics of the thermal degradation of poly(vinyl chloride) (PVC) prepared by a living radical polymerization (LRP) method was performed and compared with the results obtained from PVC prepared by the conventional free-radical process (FRP). Both differential and integral isoconversional methods were applied for determining the apparent activation energy of the dehydrochlorination stage. This study made clear noticeable differences in the thermal degradation of the PVC samples under analysis. The newly synthesized LRP-PVC material has a better thermal stability and presents substantial differences in the macroscopic kinetics of the dehydrochlorination process compared with conventional FRP-PVC. These differences were assessed in quantitative terms on the basis of the kinetic triplet [E_a,A,f(α)].     

Magnetic,optical and electrical properties of Mn-doped CuCrO<Subscript>2</Subscript> thin films prepared by chemical solution deposition method

CuCrO₂ and CuCrO₂:Mn thin films were prepared on sapphire substrates by chemical solution deposition method. The effects of the annealing temperatures and Mn concentration on the structural, electrical and optical properties were investigated. The X-ray diffraction measurement was used to confirm the c-axis orientation of CuCrO₂ and CuCrO₂:Mn thin films. The maximum transmittances of the films in the visible region are about 65% with direct band gaps of 3.25 eV. All films showed the p-type conduction and semiconductor behavior. The electrical conductivity decreases rapidly with the increase of Mn content, the maximum of the electrical conductivity of 1.35 × 10⁻² S cm⁻¹ is CuCrO₂ film deposited at 600 °C temperature in 10⁻³ Torr vacuum, which is about four orders of magnitude higher than that of the Mn-doped CuCrO₂ thin film. The energy band of the samples is constructed based on the grain-boundary scattering in order to investigate the conduction mechanism. Moreover, the samples exhibit a clear ferromagnetism, which was likely ascribed to originating from the double-exchange interaction between the Mn³⁺ and Cr³⁺ ions.     

Study of the properties of in situ Pt-doped SnO2 thin films prepared by metal-organic chemical vapour deposition

Pt-SnO₂ thin films were directly deposited by MOCVD in the temperature range 320–440°C using the reactive gas mixture SnEt4/O₂/Pt(hfa)₂ (hfa being bis(1,1,1,5,5,5-hexafluoroacetylacetonato). The Pt content of the films increases by increasing either the Pt(hfa)₂ mole fraction or the growth temperature. Platinum is uniformly incorporated through the thickness of the films although a small excess was found on the surface. In as-deposited films, Pt is in the metallic form on the surface whereas it is mainly in the form of PtO in the bulk of the layers. Pt doping decreases the resistivity by more than an order of magnitude and improves the thermal stability of the films. The detection sensitivity to ethanol in dry air of in situ Pt-doped SnO₂ is significantly enhanced compared to undoped layers. Another beneficial effect of Pt doping is the lowering of the optimum detection temperature of ethanol.     

XPS depth profiling investigations on La2Zr2O7 layers prepared by chemical solution deposition

La₂Zr₂O₇ (LZO) layers have been recently investigated as potential buffer layers for superconducting YBa₂Cu₃O_7–x coated conductors deposited on Ni tapes. Chemical solution deposition was used for LZO layer preparation. X-ray photoelectron spectroscopy (XPS) depth profiling is demonstrated to be an important method for layer characterization in addition to X-ray diffraction techniques. XPS measurements revealed layers that are homogeneous in depth, very smooth, and have no significant impurities. A slight difference to the nominal La:Zr stoichimetry is discussed in combination with structural defects that are suspected from spectral changes during ion sputtering.