The influence of annealing temperatures on the properties of Bi2VO5.5/LaNiO3/Si thin films

Bi₂VO_5.5 ferroelectric thin films were fabricated on LaNiO₃/Si(100) substrate via chemical solution deposition. Ferroelectric and dielectric properties of the thin films annealed at 500-700 °C were studied. The thin film annealed at 700 °C exhibited more favorable ferroelectric and dielectric properties than those annealed at lower temperatures. The values of remnant polarization 2P_r and coercive field E_c for the film annealed at 700 °C are 10.62 µC/cm² and 106.3 kV/cm, respectively. The leakage current of the film is about 1.92 × 10^− 8 A/cm² at 6 V. The possible mechanism of the dependence of electrical properties of the films on the annealing temperature was discussed.     

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.     

Leakage current characteristics of Bi3.15Nd0.85Ti3 − xZrxO12 thin films

Thin films of Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) and Bi_3.15Nd_0.85Ti_3 − xZr_xO₁₂ (BNTZ_x, x = 0.1 and 0.2) were fabricated on Pt/TiO₂/SiO₂/Si(100) substrates by a chemical solution deposition (CSD) technique at 700 °C. Structures, surface morphologies, leakage current characteristics and Curie temperature of the films were studied as a function of Zr ion content by X-ray diffraction, atomic force microscopy, ferroelectric test system and thermal analysis, respectively. Experimental results indicate that Zr ion substitution in the BNT film markedly decreases the leakage current of the film, while almost not changing the Curie temperature of the film, which is at about 420-460 °C. The decrease of the leakage current in BNTZ_x films is that the conduction by the electron hopping between Ti⁴⁺ and Ti³⁺ ions is depressed because Zr⁴⁺ ions can block the path between two adjacent Ti ions and enlarge hopping distance.     

Electrospun mesoporous W-doped TiO2 thin films for efficient visible-light photocatalysis

Mesoporous W⁶⁺-doped TiO₂ thin films photocatalysts were prepared via electrospinning and sol-gel chemistry, employing a triblock copolymer as structure-directing agent, and were characterized by SEM, TEM, XRD as well as N₂ adsoption/desorption isotherm. The photocatalytic activity of the films was investigated by employing the methylene blue (MB) as probe. In this study, 3% was the most suitable content of W⁶⁺ in TiO₂, at which the recombination of photoinduced electrons and holes could be effectively inhibited. In the mean time, making the photocatalysts at nanoscale and with mesopores in the films could produce more reactive sites to adsorbe and oxidize pollutants.     

Low-temperature growth and orientational control in RuO2 thin films by metal-organic chemical vapor deposition

For growth temperatures in the range of 275°C to 425°C, highly conductive RuO₂ thin films with either (110)- or (101)-textured orientations have been grown by metal-organic chemical vapor deposition (MOCVD) on both SiO₂/Si(001) and Pt/Ti/SiO₂/Si(001) substrates. Both the growth temperature and growth rate were used to control the type and degree of orientational texture of the RuO₂ films. In the upper part of this growth temperature range ( 350°C) and at a low growth rate (< 3.0 nm/min.), the RuO₂ films favored a (110)-textured orientation. In contrast, at the lower part of this growth temperature range ( 300°C) and at a high growth rate (> 3.0 nm/min.), the RuO₂ films favored a (101)-textured orientation. In contrast, higher growth temperatures (> 425°C) always produced randomly-oriented polycrystalline films. For either of these low-temperature growth processes, the films produced were crack-free, well-adhered to the substrates, and had smooth, specular surfaces. Atomic force microscopy showed that the films had a dense microstructure with an average grain size of 50–80 nm and a rms. surface roughness of 3–10 nm. Four-probe electrical transport measurements showed that the films were highly conductive with resistivities of 34–40 μΩ-cm (at 25°C).     

High-temperature anomalies of dielectric constant in TiO2 thin films

Anatase and rutile TiO₂ thin films were prepared by chemical vapor deposition with precursors Ti(OPrⁱ)₄ and Ti(dpm)₂(OPrⁱ)₂ (dpm = 2,2,6,6-tetramethylheptane-3,5-dione and Prⁱ = isopropyl), respectively. The dielectric properties of TiO₂ thin films have been studied in 20-1100 K temperature range in air, in controlled Ar/O₂ atmospheres, and in vacuum with silicon-based metal-insulator-semiconductor Au/TiO₂/Si capacitors. High-temperature (T_c ∼ 980 K) anomalous behavior of dielectric constant was observed in both anatase and rutile TiO₂ thin films.     

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.     

Preparation and visible-light-driven photoelectrocatalytic properties of boron-doped TiO2 nanotubes

In the present study, chemical vapour deposition (CVD) was applied to dope boron into TiO₂ nanotubes anodized Ti in C₂H₂O₄·2H₂O + NH₄F electrolyte with the goal of improving the photocatalytic (PC) activity under visible light. The undoped TiO₂ nanotubes had a highly self-organized structure. However, after doping through CVD, TiO₂ nanotubes suffered from an observable disintegration of morphological integrity. X-ray diffraction (XRD) results confirmed that annealing temperature had an influence on the phase structure and boron impurities could retard anatase–rutile phase transition. Diffuse reflectance absorption spectra (DRS) analysis indicated that B-doped samples displayed stronger absorption in both UV and visible range. B-doped TiO₂ nanotubes electrode annealed at 700 °C through CVD showed higher photoelectrocatalytic (PEC) efficiency in methyl orange (MO) degradation than that annealed at 400 °C and 550 °C. MO degradation was substantially enhanced with the increasing applied bias potential. Moreover, there was a synergetic effect between the electrochemical and photocatalytic processes, and the synergetic factor R reached 1.45. B-doped TiO₂ nanotubes electrode showed good stability after 10 times by repeating photoelectrocatalysis of MO.     

Photocatalysis and characterization of the gel-derived TiO2 and P-TiO2 transparent thin films

The gel-derived TiO₂ and P-TiO₂ transparent films coated on fused-SiO₂ substrates were prepared using a spin-coating technique. Effects of phosphorus dopants and calcination temperature on crystal structure, crystallite size, microstructure, light transmittance and photocatalytic activity of the films were investigated. By introducing P atoms to Ti-O framework, the growth of anatase crystallites was hindered and the crystal structure of anatase-TiO₂ could withstand temperature up to 900 °C. The photocatalytic activities of the prepared films were characterized using the characteristic time constant (τ) for the photocatalytic reaction. The titania film with a smaller τ value possesses a higher photocatalytic ability. After exposing to 365-nm UV light for 12 h, the P-TiO₂ films calcined between 600 °C and 900 °C can photocatalytically decomposed ≥ 84 mol% of the methylene blue in water with corresponding τ ≤ 7.1 h, which were better than the pure TiO₂ films prepared at the same calcination temperature.     

Solar cells with Sb2S3 absorber films

CdS/Sb₂S₃/PbS structures were prepared by sequential chemical deposition of CdS, Sb₂S₃ and PbS thin films on TEC-8 (Pilkington) transparent electrically conductive SnO₂ (TCO) coatings. CdS thin films (100 nm) were deposited with hexagonal structure from Cd-citrate bath and of cubic structure from Cd-ammine/triethanolamine bath. Sb₂S₃ thin films were deposited at 40 °C from a solution mixture of potassium antimony tartrate, triethanolamine, ammonia and thioacetamide(TA) or at 1 to 10 °C from a mixture of antimony trichloride and thiosulfate (TS). These films were made photoconductive by heating at temperatures 250 to 300 °C. When heated in the presence of a chemically deposited Se thin film of 300 nm, a solid solution Sb₂S_1.8Se_1.2 resulted. PbS thin films of 100-200 nm thickness were deposited on the TCO/CdS/Sb₂S₃ or TCO/CdS/Sb₂S_1.8Se_1.2 structure. Graphite paint was applied on the PbS film prior to applying a silver epoxy paint. The cell structures were of area 0.4 cm². The best results reported here is for a cell: TCO/CdS(hex-100 nm)/Sb₂S₃(TS-100 nm)/PbS(200 nm) with open circuit voltage (V_oc) 640 mV, short circuit current density 3.73 mA/cm², fill factor 0.29, and conversion efficiency 0.7% under 1000 Wm^− 2 sunlight. Four series-connected cells of area 1 cm² each gave V_oc of 2 V and short circuit current of 1.15 mA.     

TiO2 thin films for dyes photodegradation

The aim of the present study is to investigate the influence of the TiO₂ specific surface (powder, film) on the photocatalytic degradation of methyl orange. Porous TiO₂ films were deposited on transparent conducting oxide substrates by spray pyrolysis deposition. The films were characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy, and the UV-Vis spectroscopy. The XRD spectra of nanoporous TiO₂ films revealed an anatase, crystalline structure that is known as the most suitable structure in photocatalysis. The average thickness of the films was 260 nm and the measured band gap is 3.44 eV. The influence of the operational parameters (dye concentration, contact time) on the degradation rate of the dye on TiO₂ was examined. There were calculated the kinetic parameters and the process efficiency. Using thin films of TiO₂ is technologically recommended but raises problems due to lowering the amount of catalyst available for the dye degradation.     

Cr-doped TiO2 thin films deposited by RF-sputtering

Cr-doped TiO₂ thin films with different band gaps were prepared. Higher Cr doping was beneficial to the formation of the rutile-TiO₂ phase over the anatase-TiO₂ phase. A 4.8% Cr-doped thin film indicated a band gap of 2.95 eV, which was lower than the band gap of the rutile-TiO₂. Cr doping was accompanied by the formation of not only the rutile-TiO₂ phase but also the Cr₂O₃ phase, lead to the degradation of the hydrophilicity. The TiO₂ thin films with the mixed phase were not desirable to improve the hydrophilicity.     

Characterization of ZnO-In2O3 transparent conducting films by pulsed laser deposition

Transparent conducting oxide (TCO) films in the ZnO-In₂O₃ system were prepared by a pulsed laser deposition method. A target that consists of the mixture of ZnO and In₂O₃ powders was used. Influences of the target composition x (x = [Zn]/([Zn] + [In])) and heater temperature on structural, electrical and optical properties of the TCO films were examined. Introduction of oxygen gas into the chamber during the deposition was necessary for improvement in the transparency of the deposited films. The amorphous phase was observed for a wide range of x = 0.20-0.60 at 110 °C. Minimum resistivity was 2.65 × 10⁻⁴ Ω cm at x = 0.20. The films that showed the minimum resistivity had an amorphous structure and the composition shifted toward larger x, as the substrate temperature increased. The films were enriched in indium compared to the target composition and the cationic In/Zn ratio increased as the substrate temperature was increased.     

Precursor chemistry for the solution deposition of epitaxial La0.66Sr0.33MnO3 (LSMO) thin films

A new chemical solution deposition method for the epitaxial growth of La_0.66Sr_0.33MnO₃ (LSMO) thin films from metal acetates, acetylacetonates and propionic acid is presented. Using this method, epitaxial LSMO thin films were grown on (001) SrTiO3 (STO) single crystalline substrates in the temperature range from 800 °C to 1100 °C, both in air and in oxygen atmosphere. The LSMO thin films exhibit good structural and electrical properties. The FWHM of the ω-scan for the (002) peak has a mean value of 0.06°. The Curie temperature of the LSMO thin films is about 320 K and 350 K for the annealed in oxygen and air, respectively.     

Characterization and optoelectronic properties of sol-gel-derived CuFeO2 thin films

In this study, CuFeO₂ thin films were deposited onto quartz substrates using a sol-gel and a two-step annealing process. The sol-gel-derived films were annealed at 500 °C for 1 h in air and then annealed at 600 to 800 °C for 2 h in N₂. X-ray diffraction patterns showed that the annealed sol-gel-derived films were CuO and CuFe₂O₄ phases in air annealing. When the films were annealed at 600 °C in N₂, an additional CuFeO₂ phase was detected. As the annealing temperature increased above 650 °C in N₂, a single CuFeO₂ phase was obtained. The binding energies of Cu-2p_3/2, Fe-2p_3/2, and O-1s were 932.5 ± 0.1 eV, 710.3 ± 0.2 eV and 530.0 ± 0.1 eV for CuFeO₂ thin films. The chemical composition of CuFeO₂ thin films was close to its stoichiometry, which was determined by X-ray photoelectron spectroscopy. Thermodynamic calculations can explain the formation of the CuFeO₂ phase in this study. The optical bandgap of the CuFeO₂ thin films was 3.05 eV, which is invariant with the annealing temperature in N₂. The p-type characteristics of CuFeO₂ thin films were confirmed by positive Hall coefficients and Seebeck coefficients. The electrical conductivities of CuFeO₂ thin films were 0.28 S cm^− 1 and 0.36 S cm^− 1 during annealing at 650 °C and 700 °C, respectively, in N₂. The corresponding carrier concentrations were 1.2 × 10¹⁸ cm^− 3 (650 °C) and 5.3 × 10¹⁸ cm^− 3 (700 °C). The activation energies for hole conduction were 140 meV (650 °C) and 110 meV (700 °C). These results demonstrate that sol-gel processing is a feasible preparation method for delafossite CuFeO₂ thin films.     

Ferroelectric properties of Mn-Doped Bi3.15Nd0.85Ti3O12 thin films prepared under different annealing conditions

Mn-doped Bi_3.15Nd_0.85Ti₃O₁₂ (BNTM) thin films were fabricated on Pt/Ti/SiO₂/Si(100) substrates by a chemical solution deposition technique and annealed at different temperatures from 650 to 800 °C. The structures of the films were analyzed using X-ray diffraction, which showed that the BNTM films exhibit polycrystalline structures and random orientations. The surface morphologies of the samples were investigated using scanning electron microscopy. The average grain size of the films increases with increasing annealing temperature. Electrical properties such as remanent polarization (2P_r) are quite dependent on the annealing temperature of BNTM films. It is found that the film annealed at 750 °C exhibits excellent ferroelectricity with a remanent polarization of 2P_r = 89.3 μC/cm² and a coercive field of E_c = 99.2 kV/cm respectively.     

Preparation and super-hydrophilic properties of TiO2/SnO2 composite thin films

SnO₂-TiO₂ composite thin films were fabricated on soda-lime glass with sol-gel technology. By measuring the contact angle of the film surface and the degradation of methyl orange, we studied the influence of SnO₂ doping concentration, heat-treatment temperature and film thickness on the super-hydrophilicity and photocatalytic activity of the composite films. The results indicate that the doping of SnO₂ into TiO₂ can improve their hydrophilicity and photocatalytic activity, and the composite film with 1-5 mol% SnO₂ and heat-treated at 450°C is of super-hydrophilicity. The optimal SnO₂ concentration for the photocatalytic activity is 10 mol% and larger film thickness is helpful to reduce the contact angle of the composite films.     

TiO2/Au/TiO2 multilayer thin films: Novel metal-based transparent conductors for electrochromic devices

Transparent conductors based on Au films, with thicknesses in the 2.6 < d < 9.8 nm range, were made by DC magnetron sputtering onto glass. The films went from an “island” structure at low thicknesses to a uniform structure at d > 8 nm, as seen from electron microscopy, electrical resistance, and spectrophotometric transmittance and reflectance. Optical data for uniform films were given a consistent interpretation within the Drude model. Optimized TiO₂/Au/TiO₂ films, with a luminous transmittance of 80%, were found to have good electrochemical durability and may be useful for applications in electrochromic devices.     

Studies on chemically deposited CuInSe2 thin films

Nanocrystalline thin films of CuInSe₂ have been prepared by chemical bath deposition technique at temperatures below 60 °C. X-ray diffraction of the films confirmed the identity of CuInSe₂ and with largely broadened peaks indicated the nanocrystalline nature of the films. Images from scanning electron microscope represented spherical nanoparticles.     

Structural and electrochromic properties of TiO2 thin films prepared by metallorganic chemical vapor deposition

Titanium dioxide thin films were deposited by Metallorganic Chemical Vapor Deposition at substrate temperatures ranging from 250 °C to 450 °C over soda lime glass and indium tin oxide coated glass substrates. X-ray diffraction studies show that films have a crystalline anatase structure at all the deposition temperatures. Particle size decreases and texture changes with the increase in substrate temperature. X-ray photoelectron spectroscopy confirms the appearance of a new well resolved state in the core level of Ti 2p spectrum shifted by 1.16 eV to lower binding energy due to the reduction of Ti^+ 4 to Ti^+ 3 upon litheation. Chronoamperometery, cyclic voltammetery and in situ UV-Vis spectrophotometeric studies were carried out on the prepared samples. Particle size and crystallinity control the electrochromic performance. The 350 °C film shows the highest ion storage capacity and the highest optical modulation along with an appreciable band gap broadening.