Investigation of nozzle shape effect on Sm0.1Ce0.9O1.95 thin film prepared by electrostatic spray deposition

Dense samarium doped ceria (SDC) thin films are deposited using electrostatic spray deposition (ESD) technique. The influences of nozzle shape on the distribution of liquid jet at the nozzle tip and the morphology of the deposited SDC films are elucidated. Geometries of three nozzles employed are flat, sawtooth and wedge tips. From the observation of jet formation, the nozzle in flat shape gives the highest distribution of emitted droplets. The deposited films are characterized using a combination of XRD, SEM and AFM techniques. XRD results reveal that the single-phase fluorite structure forms at a relatively low deposition temperature of 400 °C. The flat spray tip provides the most uniform and smooth thin films, and also presents the lowest agglomeration of particles on thin-film surface.     

Synthesis of epitaxial BaZrO3 thin films by chemical solution deposition

This work reports on the low temperature preparation and characterization of BaZrO₃ (BZO) epitaxial thin films by chemical solution deposition (CSD). The X-ray θ-2θ scan and φ-scan measurements have demonstrated that the BZO films exhibit cube-on-cube epitaxy on (100) MgO substrates, with the full width at half maximum (FWHM) for the ω-scan and φ-scan of 0.35° and 0.46°, respectively. The SEM and AFM analyses revealed that the morphology of the films is strongly correlated with annealing temperature. The root mean square roughness for the film annealed at 600 °C is 3.63 nm, while for the film grown at 1000 °C is 5.25 nm.     

Fabrication of scandium stabilized zirconia thin film by electrostatic spray deposition technique for solid oxide fuel cell electrolyte

A cost-effective and promising simple deposition method, electrostatic spray deposition (ESD), was used to fabricate dense scandium stabilized zirconia (ScSZ) thin films. The effect of solvent mixtures on their surface morphology was investigated. The films deposited using a mixed ethanol-butyl carbitol solvent with high boiling point showed higher smoothness compared with those deposited using ethanol and a mixture of ethanol and ethylene glycol, respectively. Single-phase ScSZ dense films were formed within 2 h at a low deposition temperature of 450 °C. Analysis of as heat-treated films using scanning electron microscope and atomic force microscope also indicated the formation of the uniform, smooth and dense thin films even at a low densification temperature. Furthermore, the ScSZ film deposited under the optimal condition showed the maximum in electrical conductivity of approximately 0.33 S cm^− 1 at a low operating temperature of 800 °C.     

Thin films of In2O3 by atomic layer deposition using In(acac)3

Thin films of indium oxide have been deposited using the atomic layer deposition (ALD) technique using In(acac)₃ (acac = acetylacetonate, pentane-2,4-dione) and either H₂O or O₃ as precursors. Successful growth using In(acac)₃ is contradictory to what has been reported previously in the literature [J.W. Elam, A.B.F. Martinson, M.J. Pellin, J.T. Hupp, Chem. Mater. 18 (2006) 3571.]. Investigation of the dependence of temperature on the deposition shows windows where the growth rates are relatively unaffected by temperature in the ranges 165–200 °C for In(acac)₃ and H₂O, 165–225 °C for In(acac)₃ and O₃. The growth rates obtained are of the order 20 pm/cycle for In(acac)₃ and H₂O, 12 pm/cycle for In(acac)₃.     

Fabrication of YSZ thin films from suspension by electrostatic spray deposition

This work describes a novel fabrication technique to prepare yttria-stabilized zirconia (YSZ) thin films by electrostatic spray deposition (ESD) from suspension. A detailed discussion on the formulation of colloidally stable suspension to prepare dense and uniform YSZ thin films is presented in this study. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to analyze the structure and morphology of the YSZ thin films. The results show that a mixture of acetylacetone and ethanol in a ratio of 1:1 by volume is an effective suspension medium for YSZ fine particles to produce colloidally stable suspension, and the YSZ thin films with uniform in thickness about 2 μm and densely packed can be obtained by ESD from the suspension.     

Tungsten trioxide thin films prepared by electrostatic spray deposition technique

Tungsten trioxide (WO₃) thin films deposited on a Pt-coated alumina substrate using the electrostatic spray deposition (ESD) technique is reported in this paper. As precursor solution, tungsten (VI) ethoxide in ethanol was used. The morphology and the microstructure of the films were studied using scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Dense to porous morphologies were obtained by tuning the deposition temperature. Impedance spectroscopy and current-voltage measurements were used to study the electrical behaviour of the films in air, in temperature range 300-500 °C. The activation energy was estimated from Arrhenius plots. Considering the obtained results, the ESD technique proved to be an effective technique for the fabrication of porous tungsten trioxide thin films.     

Epitaxial growth of CeO2/yttria-stabilized ZrO2 double layer films on biaxially textured Ni tape via electrostatic spray assisted vapour deposition

Epitaxial growth of CeO₂ and yttria-stabilized ZrO₂ (YSZ) double layer films has been successfully carried out on biaxially textured nickel substrates at a temperature between 400 and 600 °C using electrostatic spray assisted vapour deposition method. The structure of the double layer was characterized by X-ray diffraction and scanning electron microscopy. The results show that highly oriented CeO₂/YSZ double buffer films were formed epitaxially onto biaxially textured Ni substrates. The orientation relationships between YSZ layer and Ni substrate are 001_YSZ//001_Ni and 110_YSZ//100_Ni, while the orientation relationships between CeO₂ and YSZ are 001_CeO2//001_YSZ and 100_CeO2//100_YSZ.     

Evaluation of different deposition conditions on thin films deposited by electrostatic spray deposition using a uniformity test

Copper indium disulphide films were produced by electrostatic spray deposition using a water/alcohol solution of copper chloride (CuCl₂), indium chloride (InCl₃) and thiourea (CS(NH₂)₂) sprayed onto SnO₂:F coated glass substrates. The influence of various deposition parameters, namely substrate temperature (380-450 °C), applied voltage (12-18 kV), solution concentration (0.21-0.49 M), flow rate (25-200 μl/min) and needle-substrate distance (40-70 mm) were investigated. particle image velocimetry measurements were made of the spray cone and correlated with the film uniformity. The film uniformity was measured using an optically based test developed in-house. Results show that the highest concentrated spray solution and lowest deposition temperature produce non-uniform films. In contrast, a needle-substrate distance of 50 mm, and the lowest applied voltage and flow rate resulted in the most uniform films.     

Growth of La2Mo2O9 films on porous Al2O3 substrates by radio frequency magnetron sputtering

Synthesis conditions of La₂Mo₂O₉ thin film by radio frequency (RF) sputtering technique on Al₂O₃ ceramic substrates are studied. It is found that the deposition temperature and oxygen partial pressure are the most important factors for obtaining pure La₂Mo₂O₉ films. Varying both parameters, Mo-rich, stoichiometric, and Mo-deficient films are obtained. With increasing the La:Mo ratio, films become denser. A crust layer is observed on top of the Mo-rich and the Mo-deficient films. The formation of the La₂Mo₂O₉ phase is discussed with respect to the sputtering mechanism.     

Growth and characterisation of CaCu2Ox thin films by pulsed injection MOCVD

Oxides with the structure MCu₂O₂ (M = Ca, Ba, Mg and Sr) are promising materials for the development of new p-type transparent conducting oxide thin films. This paper reports preliminary results on the growth and characterisation of CaCu₂O_x thin films by pulsed injection MOCVD. By using as precursors calcium and copper tetramethylheptanedionate dissolved in meta-xylene, mixed calcium-copper films have been grown in the temperature range from 450 °C to 550 °C. At these temperatures, deposited films exhibited a high mirror reflection effect, good adherence and were reasonably uniform with the cationic composition of the films being easily controlled by adjusting the copper-calcium ratio in the precursor solution. In CaCu₂O₂, copper is in the Cu¹⁺ oxidation state and depending on the oxygen partial pressure used, the films either contained CaCu₂O₃ or a mixture of CaO, CuO and Cu₂O. Optimisation of annealing conditions increased the presence of Cu¹⁺ in the film. Films had a maximum transmittance of 50% in the visible range and were highly resistive. Appropriate annealing conditions reduced the resistivity of the films.     

Epitaxial growth of RuO2 thin films by metal-organic chemical vapor deposition

Conductive RuO₂ thin films were epitaxially grown on LaAlO₃(100) and MgO(100) substrates by metal-organic chemical vapor deposition (MOCVD). The deposited RuO₂ films were crack-free, and well adhered to the substrates. The RuO₂ film is (200) oriented on LaAlO₃ (100) substrates at deposition temperature of 600°C and (110) oriented on MgO(100) substrates at deposition temperature of 350°C and above. The epitaxial growth of RuO₂ on MgO and LaAlO₃ is demonstrated by strong in-plane orientation of thin films with respect to the major axes of the substrates. The RuO₂ films on MgO(100) contain two variants and form an orientation relationship with MgO given by RuO₂(110)//MgO(100) and RuO₂[001]//MgO[011]. The RuO₂ films on LaAlO₃(100), on the other hand, contain four variants and form an orientation relationship with LaAlO₃ given by RuO₂(200)//LaAlO₃(100) and RuO₂[011]//LaAlO₃[011]. Electrical measurements on the RuO₂ thin films deposited at 600°C show room-temperature resistivities of 40 and 50 μΩ cm for the films deposited on the MgO and LaAlO₃ substrates, respectively.     

La2Zr2O7 films on Cu–Ni alloy by chemical solution deposition process

Films of La₂Zr₂O₇ (=LZO) have been formed by chemical solution deposition technique (CSD) on new bi-axially textured Cu–Ni alloy tapes based on rolled constantan (Cu₅₅Ni₄₅) Rabits. The precursor used was acetylacetonates treated in propionic acid (0.1–0.87 mol/l) and then deposited by spin-coating. The LZO film starts to crystallize above 850 °C, the film nucleates bi-axially textured on the substrate (with unit cell axis rotated 45° from those of the substrate). The top part of the film is not textured even after long annealing time at 1100 °C, but the interfacial part is bi-axially textured. Thus, synthesis of bi-axially textured films on Cu₅₅Ni₄₅ Rabits seems possible but more works are needed to optimize its properties.     

Characterization of Al2O3/ZrO2 nano multilayer thin films prepared by pulsed laser deposition

Microstructural characterization of pulsed laser deposited Al₂O₃/ZrO₂ multilayers on Si (1 0 0) substrates at an optimized oxygen partial pressure of 3 × 10⁻² mbar and at room temperature (298 K) has been carried out. A nanolaminate structure consisting of alternate layers of ZrO₂ and Al₂O₃ with 40 bi-layers was fabricated at different zirconia layer thicknesses (20, 15 and 10 nm). The objective of the work is to study the effect of ZrO₂ layer thickness on the stabilization of tetragonal ZrO₂ phase for a constant Al₂O₃ layer thickness of 5 nm. The Al₂O₃/ZrO₂ multilayer films were characterized using high temperature X-ray diffraction (HTXRD) in the temperature range 298–1473 K. The studies showed that the thickness of the zirconia layer has a profound influence on the crystallization temperature for the formation of tetragonal zirconia phase. The tetragonal phase content increased with the decrease of ZrO₂ layer thickness. The cross-sectional transmission electron microscope (XTEM) investigations were carried out on a multilayer thin films deposited at room temperature. The XTEM studies showed the formation of uniform thickness layers with higher fraction of monoclinic and small fraction of tetragonal phases of zirconia and amorphous alumina.     

Synthesis of SrSnO3 thin films by pulsed laser deposition: Influence of substrate and deposition temperature

SrSnO₃ thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO₃ and (100)SrTiO₃. High quality epitaxial (100) oriented films were obtained on LaAlO₃ and SrTiO₃ while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO₃ from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations.     

Annealing effects of In2O3 thin films on electrical properties and application in thin film transistors

Considering practical applications in electronic devices, we studied the growth of In₂O₃ thin films on amorphous glasses by magnetron sputtering at room temperature and annealing effect on the structural and electrical properties. The vacuum annealed In₂O₃ thin films display a grain size enlargement and preferential orientation. Electrical characterization shows that the vacuum annealed In₂O₃ thin films exhibit a significant enhancement of both electron density and mobility, while air ambient annealing leads to a remarkable drop. The mechanism of the electrical characteristic changes in In₂O₃ thin films by annealing is explored by using different scattering mechanisms. Finally, a thin film transistor device using vacuum annealed In₂O₃ nano-meter thin films as active channel material is demonstrated.     

Fluorescent tags to visualize defects in Al2O3 thin films grown using atomic layer deposition

Defects and cracks in thin film barriers that are coated on polymers allow the leakage of reactive species through the polymer substrate. Fluorescent tags have been developed to visualize defects and cracks in thin film barriers and to inspect rapidly the barrier quality with minimal sample preparation. For Al₂O₃ films with a thickness of 25 nm deposited on polyethylene naphthalate polymer substrates using atomic layer deposition techniques, the fluorescent tags have identified cracks ~ 20 nm in width after applied strain and have observed individual defects as small as ~ 200 nm in diameter.     

Structure, properties and gas sensing behavior of Cr2 − xTixO3 films fabricated by electrostatic spray assisted vapour deposition

Single-phase eskolaite crystalline Cr_2 − xTi_xO₃ films (CTO) with a uniform porous microstructure were fabricated via an electrostatic spray assisted vapour deposition (ESAVD) method. The sensing behavior upon exposure to ammonia and ethanol was characterized in a CTO film-based sensor device in terms of response, reproducibility, humidity constraints and sensor stability. The ESAVD process has been shown to be capable of producing CTO films at low temperature (650 °C) and more importantly, it results in a more uniform titanium distribution and better microstructural control than processes based on solid-state chemical reactions. The material with a nominal composition of Cr_1.7Ti_0.3O₃ exhibited the highest sensitivity among the different Cr_2 − xTi_xO₃ compositions examined towards ammonia over the temperature range of 200-500 °C with a peak sensitivity of 2.90 at 200 °C. The CTO materials, when used as sensors, also exhibit excellent responses to ethanol concentration in air. The sensitivity was 0.64 for 10 ppm ethanol, 0.85 for 25 ppm, and 0.92 for 50 ppm, respectively.     

Preparation of SnO2 thin films at low temperatures with H2 gas by the hot-wire CVD method

H₂ additional effect for crystallization of SnO₂ films prepared by the hot-wire CVD method was investigated. The crystallization of SnO₂ films starts at 170 °C. The selectivity enhancement of the solar cell substrate will contribute to reduce the cost of silicon thin film solar cells. The atomic hydrogen assisted nano-crystallization exists for the depositions of SnO₂ films by the hot-wire CVD method. Furthermore, the addition of H₂ gas improved the electrical conductivity up to 5.3 × 10⁰ S/cm. However, these effects are limited in the deposition condition of a small amount of hydrogen. Addition of much higher hydrogen concentration starts an etching effect of oxygen atoms.     

Composition dependence of structural and optical properties of Ba(Zrx,Ti1-x)O3 thin films grown on MgO substrates by pulsed laser deposition

Ba(Zr_x,Ti_1-x)O₃ (BZT) films with Zr concentration ranging from 0 to 40% were grown on MgO single crystal substrates by pulsed laser deposition, and their optical properties in the visible range were systematically characterized. A linear increase in the out-of-plane lattice constant of BZT unit cell with increasing Zr content was detected by X-ray diffraction. The surface morphology was observed by atomic force microscopy and the grain size was shown to increase with Zr concentration. Prism coupling and UV-visible transmission spectroscopy techniques were used to analyze the optical properties of the films. Refractive index between 2.15 and 2.3 was observed at 633 and 1547 nm respectively, which decreased with rising Zr content. The BZT films also possessed large optical band gap energy up to 3.92 eV, which increased with rising Zr content. Quadratic electro-optic effect was observed with electro-optic coefficients between 0.11 and 0.81 × 10^− 18 m²/V², which decreased with Zr concentration. Optical loss was estimated from scattering and absorption, and the absorption coefficient dropped with increasing Zr content at near band gap. The obtained results provide information for the design of BZT thin film-based optical devices.     

Cr2O3 thin films grown at room temperature by low pressure laser chemical vapour deposition

Chromia (Cr₂O₃) has been extensively explored for the purpose of developing widespread industrial applications, owing to the convergence of a variety of mechanical, physical and chemical properties in one single oxide material. Various methods have been used for large area synthesis of Cr₂O₃ films. However, for selective area growth and growth on thermally sensitive materials, laser-assisted chemical vapour deposition (LCVD) can be applied advantageously.Here we report on the growth of single layers of pure Cr₂O₃ onto sapphire substrates at room temperature by low pressure photolytic LCVD, using UV laser radiation and Cr(CO)₆ as chromium precursor. The feasibility of the LCVD technique to access selective area deposition of chromia thin films is demonstrated. Best results were obtained for a laser fluence of 120 mJ cm⁻² and a partial pressure ratio of O₂ to Cr(CO)₆ of 1.0. Samples grown with these experimental parameters are polycrystalline and their microstructure is characterised by a high density of particles whose size follows a lognormal distribution. Deposition rates of 0.1 nm s⁻¹ and mean particle sizes of 1.85 μm were measured for these films.