High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.     

Development of porous metal oxide thin films by co-evaporation

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide-tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV-vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.     

Effect of molybdenum doping on the electrochromic properties of tungsten oxide thin films by RF magnetron sputtering

Thin films of pure and molybdenum (Mo)-doped tungsten trioxide (WO₃) were deposited on indium tin oxide (ITO)-coated glass and Corning glass substrates by RF magnetron sputtering technique. The effect of Mo doping on the structural, morphological, optical and electrochromic properties of WO₃ films was studied systematically. The energy dispersive X-ray analysis (EDAX) revealed that the films consist of molybdenum concentrations from 0 to 2 at.%. X-ray diffraction (XRD) studies indicated that with the increase of Mo concentration the structural phase transformation takes place from polycrystalline to amorphous phase. The crystallite size of the films decreased from 24 to 12 nm with increase of doping concentration of Mo in WO₃. Scanning electron microscope (SEM) analysis revealed that Mo dopant led to significant changes in the surface morphology of the films. The electrochemical and electrochromic performance of the pure and Mo-doped WO₃ were studied. The WO₃ films formed with 1.3 at.% Mo dopant concentration exhibited high optical modulation of 44.3 % and coloration efficiency of 42.5 cm²/C.     

Growth and surface characterization of sputter-deposited molybdenum oxide thin films

Molybdenum oxide thin films were produced by magnetron sputtering using a molybdenum (Mo) target. The sputtering was performed in a reactive atmosphere of an argon-oxygen gas mixture under varying conditions of substrate temperature (T_s) and oxygen partial pressure (pO₂). The effect of T_s and pO₂ on the growth and microstructure of molybdenum oxide films was examined in detail using reflection high-energy electron diffraction (RHEED), Rutherford backscattering spectrometry (RBS), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. The analyses indicate that the effect of T_s and pO₂ on the microstructure and phase of the grown molybdenum oxide thin films is remarkable. RHEED and RBS results indicate that the films grown at 445 °C under 62.3% O₂ pressure were stoichiometric and polycrystalline MoO₃. Films grown at lower pO₂ were non-stoichiometric MoO_x films with the presence of secondary phase. The microstructure of the grown Mo oxide films is discussed and conditions were optimized to produce phase pure, stoichiometric, and highly textured polycrystalline MoO₃ films.     

Bandgap widening in highly conducting CdO thin film by Ti incorporation through radio frequency magnetron sputtering technique

Transparent and highly conducting thin films of cadmium oxide (CdO) with titanium doping were synthesized by using radio frequency magnetron sputtering technique. The thin films were deposited on glass and silicon substrates with different percentages of titanium at a fixed substrate temperature 473 K and a fixed pressure of 0.1 mbar in Ar atmosphere. The deposited films were characterized by studying their crystallographic structure, optical and electrical properties. X-ray diffractometer, atomic force microscope, UV–Vis–NIR spectrophotometer, and X-ray photoelectron spectrophotometer were used for different characterizations. All the films have a rock-salt structure. A systematic increase in the optical bandgap was found for the CdO thin films with Ti doping, so that it can be considered as a candidate material for different optoelectronic device applications. Electrical conductivity was also found to increase with Ti doping concentration.     

Some physical properties of In doped copper oxide films produced by ultrasonic spray pyrolysis

In this work, we have reported the effect of In doping on structural, optical and surface properties of copper oxide films obtained by a low-cost ultrasonic spray pyrolysis technique. Thicknesses, refractive indices and extinction coefficients of the films have been determined by Spectroscopic ellipsometry technique using Cauchy-Urbach model for fitting. A very good agreement was found between experimental and theoretical parameters with low MSE values. Transmission and reflectance spectra have been taken by UV Spectrophotometer, and band gap values have been determined by optical method. Structural properties of the films were investigated with X-ray diffraction patterns. In doping caused the films to growth through some certain directions. Atomic force microscope images have been taken to see the effect of In doping on surface topography and roughness of copper oxide films. Surface properties of undoped films have been improved by In doping. Lowest roughness values have been obtained for In doping at 1%. As a result, we have concluded that properties of copper oxide films which are commonly used in solar cells may have improved by In doping (especially In doped at 1%).     

Synthesis and characterisations of Au-nanoparticle-doped TiO2 and CdO thin films

In the present study, pure and gold nanoparticle (Au NP)-doped titanium dioxide (TiO₂) and cadmium oxide (CdO) thin film were prepared by the sol–gel method, and the effect of Au NP doping on the optical, structural and morphological properties of these thin films was investigated. The prepared thin films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectra. While the optical band increases from 3.62 to 3.73 for TiO₂ thin films, it decreases from 2.20 to 1.55 for CdO thin films with increasing Au doping concentration. Analysis of XRD indicates that the intensities of peaks of the crystalline phase have increased with the increasing Au NP concentrations in all thin films. SEM images demonstrate that the surface morphologies of the samples were affected by the incorporation of Au NPs. Consequently, the most significant results of the present study are that the Au NPs can be used to modify the optical, structural and morphological properties of TiO₂ and CdO thin films.     

Spray deposition of highly transparent fluorine doped cadmium oxide thin films

The cadmium oxide (CdO) and F:CdO films have been deposited by spray pyrolysis method using cadmium acetate and ammonium fluoride as precursors for Cd and F ions, respectively. The effect of temperature and F doping on the structural, morphological, optical and Hall effect properties of sprayed CdO thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption and electrical measurement techniques. TGA and DTA studies, indicates the formation of CdO by decomposition of cadmium acetate after 250 °C. XRD patterns reveal that samples are polycrystalline with cubic structure and exhibits (2 0 0) preferential orientation. Considerable broading of (2 0 0) peak, simultaneous shifting of corresponding Bragg's angle have been observed with respect to F doping level. SEM and AFM show the heterogeneous distribution of cubical grains all over the substrate, which are randomly distributed. F doping shifts the optical gap along with the increase in the transparency of CdO films. The Hall effect measurement indicates that the resistivity and mobility decrease up to 4% F doping.     

Optical constants of thin oxide films on titanium

Thin oxide films on titanium formed by heating were studied by the ellipsometric method. To obtain the complex refractive index and film thicknesses, the ellipsometric measurements were performed by means of the immersing method: each sample was measured first in air and then in a liquid of known refractive index (in our case CCl₄). The optical constants and the oxide film thickness were computed by means of a computer from two pairs of ellipsometric values. To state the optical constants of clean titanium surface the graphic-computational method was proposed and applied. The measurements were carried out at two wavelengths on oxide films grown in air and dry oxygen by thermal oxidation at temperatures from 150 to 700 °C. It has been shown that when increasing the film thickness the refractive index of the film decreases, whereas the absorption coefficient is independent on the film thickness. Optical constants of oxide films growing in dry oxygen are smaller than those growing in air.     

Fluorine-doped zinc oxide transparent and conducting electrode by chemical spray synthesis

Highly transparent and conducting fluorine-doped zinc oxide thin films, consisting of spherical nanometer-sized grains, were synthesized onto soda-lime glass substrate by using a chemical spray unit. The effect of fluorine doping concentration in starting solution was investigated. Both doped and undoped films were preferentially oriented along [002] direction. Electrical resistivity decreases from 5.7 x 10^-2 to 8.6 x 10^-3 ohm-cm after 1 at.% fluorine doping, and increases for higher doping concentration. However, surface morphology of films obtained at 3 at.% fluorine doping appeared smooth and uniform. A shift of the edge of the optical transmission in the ultraviolet region as a result of fluorine doping was obtained.     

The role of W doping in response of hydrogen sensors based on MAO titania films

Anatase TiO₂ and W doped TiO₂ films were fabricated by micro-arc oxidation (MAO) on titanium substrates and their hydrogen sensing properties were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the oxide films and electrochemical impedance spectroscopy (EIS) was applied to investigate the gas sensing mechanism. It is found that the conductivity of TiO₂ films varies with the introduction of W dopant. EIS analysis reveals that the grains and especially the grain boundaries are mainly contributed to the hydrogen response and their equivalent circuits could be represented electrochemically by parallel resistor and constant phase element (CPE). The enhanced sensor signal at higher measuring temperature (300 °C) is observed with an optimal doping concentration of W ions (1.81 at.%).     

Structure and optical properties of chemically synthesized titanium oxide deposited by evaporation technique

Titanium oxide inorganic ion exchange material was synthesized by hydrolysis with water and ammonia solution. Structural feature of the synthesized titanium oxide was analyzed using X-ray diffraction, X-ray fluorescence and infrared spectrometer technique. Tentative formula of titanium oxide was determined and written as TiO₂·0.58H₂O. Titanium oxide films were deposited on glass substrates by means of an electron beam evaporation technique at room temperature from bulk sample. The films were annealed at 250, 350, 450, and 550 °C temperatures. Transmittance, reflectance, optical energy gap, refractive index and extinction coefficient were investigated. The transmittance values of 85% in the visible region and 88% in the near infrared region have been obtained for titanium oxide film annealed at 550 °C. Kubelka-Munk function was used to evaluate the absorption coefficient which was used to determine the optical band gap. It was found that the optical band gap increases with increasing annealing temperature whereas the refractive index and extinction coefficient decreases.     

Effect of antimony doping on the low‐temperature performance of solution‐processed indium oxide thin film transistors

The effects of antimony (Sb) doping on solution‐processed indium oxide (InO_x) thin film transistors (TFTs) were examined. The Sb‐doped InSbO TFT exhibited a high mobility, low gate swing, threshold voltage, and high I_ON/OFF ratio of 4.6 cm²/V s, 0.29 V/decade, 1.9 V, and 3 × 10⁷, respectively. The gate bias and photobias stability of the InSbO TFTs were also improved by Sb doping compared to those of InO_x TFTs. This improvement was attributed to the reduction of oxygen‐related defects and/or the existence of the lone‐pair s‐electron of Sb³⁺ in amorphous InSbO films. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

On the phase formation of titanium oxide thin films deposited by reactive DC magnetron sputtering: influence of oxygen partial pressure and nitrogen doping

This work describes about the control on phase formation in titanium oxide thin films deposited by reactive dc magnetron sputtering. Various phases of titanium oxide thin films were deposited by controlling the oxygen partial pressure during the sputtering process. By adding nitrogen gas to sputter gas mixture of oxygen and argon, the oxygen partial pressure was decreased further below the usual critical value, below and above which the sputtering yields metallic and oxide films, respectively. Furthermore, nitrogen addition eliminated the typical hysteretic behaviour between the flow rate and oxygen partial pressure, and significantly influenced the sputter rate. On increasing the oxygen partial pressure, the ratio between anatase and rutile fraction and grain size increases. The fracture cross-sectional scanning electron microscopy together with the complementary information from X-ray diffraction and micro-Raman investigations revealed the evolution and spatial distribution of the anatase and rutile phases. Both the energy delivered to the growing film and oxygen vacancy concentrations are correlated with the formation of various phases upon varying the oxygen partial pressure.     

Surface flatness of optical thin films evaluated by gray level co-occurrence matrix and entropy

The surface characteristics of titanium oxide films evaluated by gray level co-occurrence matrices (GLCMs) and entropy are demonstrated experimentally. A PC-based measurement system was set up to detect the interference fringe of optical coating surface as captured by a Fizeau interferometer. Titanium oxide films were prepared by an electron-beam gun evaporation method. The proposed measuring system was used to evaluate the surface flatness of titanium oxide films coated on glass substrates. The variation of entropy in titanium oxide films before and after film deposition was found to be related to the root-mean-square (rms) surface roughness. Surface characteristics of thin films were fast measured by our proposed method and the test results were verified by atomic force microscopy (AFM) and scanning electrical microscopy (SEM).     

The origin of haze in CVD tin oxide thin films

The origin of haze was investigated in antimony-doped tin oxide thin films, and in double-stack thin films of fluorine-doped tin oxide/antimony-doped tin oxide, both deposited by chemical vapor deposition onto soda-lime–silica float glass substrates. These transparent conductive oxide thin films are of great importance in the production of solar control architectural glazing units. Therefore, understanding the origins of haze is necessary to the development of coated, IR-reflecting glass windows with low overall haze levels. Haze measurements of as-prepared and polished samples were correlated with surface roughness and concentration of internal hole defects. Surface roughnesses were evaluated by atomic force microscopy, and characterized by estimated RMS values. In thin tin oxide films (<2000 Å) internal hole defects caused haze, while in thick tin oxide films (>4000 Å) surface roughness was the primary source of haze.     

Reproducibility evaluation and Al doping of sol-gel-derived single- and multi-layer zinc oxide thin films

Both single- and multi-layer thin films of sol-gel-derived undoped and Al-doped zinc oxide material systems were fabricated for potential use in transparent conducting oxide modules. Functional properties of the resultant films were characterised comparatively. High degree of reproducibility was demonstrated for the characterised properties, with the exception of the electrical conductivity. Influences of Al doping on the characterised properties were also investigated. Al doping reduced the average crystallite size, and led to a denser and less porous morphology, and also caused an increase in transparency in the UV region. Moreover, it was shown that the electrical conductivity of this thin film system could be improved upon either the application of a forming gas process, or Al doping.     

Growth of oxide thin films for optical gas sensor applications

Tungsten trioxide and titanium dioxide thin films were synthesised by pulsed laser deposition. We used for irradiations of oxide targets an UV KrF* (λ = 248 nm, τ_FWHM ≅ 20 ns, ν = 2 Hz) excimer laser source, at 2 J/cm² incident fluence value. The experiments were performed in low oxygen pressure. The (0 0 1) SiO₂ substrates were heated during the thin film deposition process at temperature values within the 300-500 °C range. The structure and crystalline status of the obtained oxide thin films were investigated by high resolution transmission electron microscopy. Our analyses show that the films are composed by nanoparticles with average diameters from a few to a few tens of nm. Moreover, the films deposited at substrate temperatures higher than 300 °C are crystalline. The tungsten trioxide films consist of a mixture of triclinic and monoclinic phases, while the titanium dioxide films structure corresponds to the tetragonal anatase phase. The oxide films average transmittance in the visible-infrared spectral range is higher than 80%, which makes them suitable for sensor applications.     

Structural, optical and electrical properties of molybdenum-doped cadmium oxide thin films prepared by spray pyrolysis method

Molybdenum-doped cadmium oxide films were prepared by a spray pyrolysis technique at a substrate temperature of 300?°C. The effect of doping on structural, electrical and optical properties were studied. X-ray analysis shows that the undoped CdO films are preferentially oriented along the (111) crystallographic direction. Molybdenum doping concentration increases the films?? packing density and reorients the crystallites along the (200) plane. A?minimum resistivity of 4.68×10^?4????cm with a maximum mobility of 75?cm²?V^?1?s^?1 is achieved when the CdO film is doped with 0.5?wt.% Mo. The band-gap value is found to increase with doping and reaches a maximum of 2.56?eV for 0.75?wt.% as compared to undoped films of 2.2?eV.     

Pulsed laser deposition of molybdenum oxide thin films

Thin films of molybdenum oxide were deposited in vacuum by pulsed laser ablation using a xenon fluoride (351 nm) and a krypton fluoride (248 nm) excimer lasers. The films were deposited on unheated substrates and were post-annealed in air in the temperature range 300–500°C. The structural, morphological, chemical, and optical properties of the films were studied. As-deposited films were found to be dark. The transparency of the films was improved with annealing in air. The films were polycrystalline with diffraction peaks that belong to the orthorhombic phase of MoO₃. The surface morphology of the films showed a layered structure. Both the grain size and surface roughness increased with annealing temperature. The stoichiometry of the films improved upon annealing in air, with the best stoichiometry of MoO_2.95 obtained for films deposited by the XeF laser and annealed at 400°C. Similarly, the best transparency, with a transmittance exceeding 80%, was obtained with the films annealed in the temperature range 400–450°C.