Structural, morphological and electrical properties of spray deposited nano-crystalline CeO2 thin films

Nanocrystalline, uniform, dense, and adherent cerium oxide (CeO₂) thin films have been successfully deposited by a simple and cost effective spray pyrolysis technique. CeO₂ films were deposited at low substrate and annealing temperatures of 350 °C and 500 °C, respectively. Films were characterized by differential thermal analysis, X-ray diffraction, scanning electron microscopy, atomic force microscopy; two probe resistivity method and impedance spectroscopy. X-ray diffraction analysis revealed the formation of single phase, well crystalline thin films with cubic fluorite structure. Crystallite size was found to be in the range of 10-15 nm. AFM showed formation of smooth films with morphological grain size 27 nm. Films were found to be highly resistive with room temperature resistivity of the order of 10⁷ Ω cm. Activation energy was calculated and found to be 0.78 eV. The deposited film showed high oxygen ion conductivity of 5.94 × 10⁻³ S cm⁻¹ at 350 °C. Thus, the deposited material shows a potential application in intermediate temperature solid oxide fuel cells (IT-SOFC) and might be useful for μ-SOFC and industrial catalyst applications.     

Effect of annealing temperature on the structure and optical properties of sputtered TiO2 films

TiO₂ thin films were deposited by DC reactive magnetron sputtering. Some TiO₂ thin films samples were annealed for 5 min at different temperatures from 300 to 900 °C. The structure and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and ultraviolet-visible (UV-vis) spectrophotometry, respectively. The influence of the annealing temperature on the structure and optical properties of the films was investigated. The results show that the as-deposited TiO₂ thin films are mixtures of anatase and rutile phases, and possess the column-like crystallite texture. With the annealing temperature increasing, the refractive index and extinction coefficient increase. When the annealing temperature is lower than 900 °C, the anatase phase is the dominant crystalline phase; the weight fraction of the rutile phase does not increase significantly during annealing process. As the annealing temperature rises to 900 °C, the rutile phase with the large extinction coefficient becomes the dominant crystalline phase, and the columnar structure disappears. The films annealed at 300 °C have the best optical properties for the antireflection coatings, whose refractive index and extinction coefficient are 2.42 and 8 × 10⁻⁴ (at 550 nm), respectively.     

Characterization of cobalt oxide thin films prepared by a facile spray pyrolysis technique using perfume atomizer

Cobalt oxide (Co₃O₄) thin films were prepared by a facile spray pyrolysis technique using perfume atomizer from aqueous solution of hydrated cobalt chloride salt (CoCl₂·6H₂O) as source of cobalt. The films were deposited onto the amorphous glass substrates kept at different temperatures (300-500 °C). The influences of molar concentration of the starting solution and substrate temperature on the structural, morphological and optical properties of (Co₃O₄) thin films were studied. It was found from X-ray diffraction (XRD) analysis that the films prepared with molar concentration greater than 0.025 M/L were polycrystalline spinel type cubic structure. The preferred orientation of the crystallites of these films changes gradually from (6 2 2) to (1 1 1) when the substrate temperature increases. By Raman spectroscopy, five Raman active modes characteristic of Co₃O₄ spinel type cubic structure were found and identified at 194, 484, 522, 620 and 691 cm⁻¹. The scanning electron microscopy (SEM) images showed micro porous structure with very fine grains less than 50 nm in diameter. These films exhibited also a transmittance value of about 70% in the visible and infra red range.     

New process for synthesis of nickel oxide thin films and their characterization

Sol-gel spin coating method has been successfully employed for the deposition of nanocrystalline nickel oxide (NiO) thin films. The films were annealed at 400-700 °C for 1 h in an air and changes in the structural, morphological, electrical and optical properties were studied. The structural properties of nickel oxide films were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis shows that all the films are crystallized in the cubic phase and present a random orientation. Surface morphology of the nickel oxide film consists of nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology. The electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 10⁻⁴ to 10⁻² (Ω cm)⁻¹ after annealing. The decrease in the band gap energy from 3.86 to 3.47 eV was observed after annealing NiO films from 400 to 700 °C. These mean that the optical quality of NiO films is improved by annealing.     

Structural, optical and electrical properties of CuIn5S8 thin films grown by thermal evaporation method

Stoichiometric compound of copper indium sulfur (CuIn₅S₈) was synthesized by direct reaction of high purity elemental copper, indium and sulfur in an evacuated quartz tube. The phase structure of the synthesized material revealed the cubic spinel structure. The lattice parameter (a) of single crystals was calculated to be 10.667 Å. Thin films of CuIn₅S₈ were deposited onto glass substrates under the pressure of 10⁻⁶ Torr using thermal evaporation technique. CuIn₅S₈ thin films were then thermally annealed in air from 100 to 300 °C for 2 h. The effects of thermal annealing on their physico-chemical properties were investigated using X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), optical transmission and hot probe method. XRD studies of CuIn₅S₈ thin films showed that as-deposited films were amorphous in nature and transformed into polycrystalline spinel structure with strong preferred orientation along the (3 1 1) plane after the annealing at 200 °C. The composition is greatly affected by thermal treatment. From the optical transmission and reflection, an important absorption coefficient exceeds 10⁴ cm⁻¹ was found. As increasing the annealing temperature, the optical energy band gap decreases from 1.83 eV for the as-deposited films to 1.43 eV for the annealed films at 300 °C. It was found that CuIn₅S₈ thin film is an n-type semiconductor at 300 °C.     

P-type transparent conducting SnO2:Zn film derived from thermal diffusion of Zn/SnO2/Zn multilayer thin films

Highly transparent, p-type conducting SnO₂:Zn thin films are prepared from the thermal diffusion of a sandwich structure of Zn/SnO₂/Zn multilayer thin films deposited on quartz glass substrate by direct current (DC) and radio frequency (RF) magnetron sputtering using Zn and SnO₂ targets. The deposited films were annealed at various temperatures for thermal diffusion. The effect of annealing temperature and time on the structural, electrical and optical performances of SnO₂:Zn films was studied. XRD results show that all p-type conducting films possessed polycrystalline SnO₂ with tetragonal rutile structure. Hall effect results indicate that the treatment at 400 °C for 6 h was the optimum annealing parameters for p-type SnO₂:Zn films which have relatively high hole concentration and low resistivity of 2.389 × 10¹⁷ cm^− 3 and 7.436 Ω cm, respectively. The average transmission of the p-type SnO₂:Zn films was above 80% in the visible light range.     

In doped ZnO thin films

ZnO thin films were deposited by ultrasonic spray technique, zinc acetate was used as starting solution with a molarity of 0.1 M. A set of indium (In) doped ZnO (between 2 and 8 wt%) thin films were grown on glass substrate at 350 °C. The present work is focused on the influence of the doping level on the structural, optical and electrical films properties. Optical film characterization was carried by using UV-visible transmission spectroscopy, the optical gap was deduced from absorption. From X ray diffraction (XRD) analysis, we have deduced that ZnO films are formed with nanocrystalline structure with preferential (0 0 2) orientation. The grain size is increased with In doping from 28 to 37 nm. Electrical characterization was achieved using two-probes coplanar structure, the measured conductivity varies from 2.3 to 5.9 Ω cm⁻¹ when increasing the doping level. However the optical gap is reduced from 3.4 to 3.1 eV.     

New process for synthesis of ZnO thin films: Microstructural, optical and electrical characterization

Nanocrystalline ZnO thin films were prepared on glass substrates by using spin coating technique. The effect of annealing temperature (400-700 °C) on structural, compositional, microstructural, morphological, electrical and optical properties of ZnO thin films were studied by X-ray diffraction (XRD), Energy dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), High Resolution Transmission Microscopy (HRTEM), Scanning Electron Microscopy (SEM), Electrical conductivity and UV-visible Spectroscopy (UV-vis). XRD measurements show that all the films are nanocrystallized in the hexagonal wurtzite structure and present a random orientation. The crystallite size increases with increasing annealing temperature. These modifications influence the optical properties. The AFM analysis revealed that the surface morphology is smooth. The HRTEM analysis of ZnO thin film annealed at 700 °C confirms nanocrystalline nature of film. The SEM results shows that a uniform surface morphology and the nanoparticles are fine with an average grain size of about 40-60 nm. The dc room temperature electrical conductivity of ZnO thin films were increased from 10⁻⁶ to 10⁻⁵ (Ω cm)⁻¹ with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of ZnO films annealed at 400-700 °C were estimated to be of the order of 4.75-7.10 × 10¹⁹ cm⁻³ and 2.98-5.20 × 10⁻⁵ cm² V⁻¹ S⁻¹.The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 3.32 eV to 3.18 eV with increasing annealing temperature between 400 and 700 °C. This means that the optical quality of ZnO films is improved by annealing.It is observed that the ZnO thin film annealing at 700 °C has a smooth and flat texture suited for different optoelectronic applications.     

Growth and characterization of chemical bath deposited Cd1−xZnxS thin films

Cd_1−xZn_xS (0 ≤ x ≤ 1) thin films have been deposited by chemical bath deposition method on glass substrates from aqueous solution containing cadmium acetate, zinc acetate and thiourea at 80 ± 5 °C and after annealed at 350 °C. The structural, morphological, compositional and optical properties of the deposited Cd_1−xZn_xS thin films have been studied by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), photoluminescence (PL) and UV-vis spectrophotometer, respectively. X-ray diffraction analysis shows that for x < 0.8, the crystal structure of Cd_1−xZn_xS thin films was hexagonal structure. For x > 0.6, however, the Cd_1−xZn_xS films were grown with cubic structure. Annealing the samples at 350 °C in air for 45 min resulted in increase in intensity as well as a shift towards lower scattering angles. The parameters such as crystallite size, strain, dislocation density and texture coefficient are calculated from X-ray diffraction studies. SEM studies reveal the formation of Cd_1−xZn_xS films with uniformly distributed grains over the entire surface of the substrate. The EDX analysis shows the content of atomic percentage. Optical method was used to determine the band gap of the films. The photoluminescence spectra of films have been studied and the results are discussed.     

LiCoO2 cathode thin film fabricated by RF sputtering for lithium ion microbatteries

Thin films of lithium cobalt oxide were deposited on Pt or Pt/Ti/quartz glass substrates by radio frequency (RF) magnetron sputtering at the substrate temperatures from room temperature to 500 °C. As the substrate temperature increased, the film structure changed from amorphous structure to crystallinity with a strong (003) texture as characterized by X-ray diffraction. The surface morphology and cross-section were observed using scanning electron microscopy. It was found that the films tended to crack at a high substrate temperature. Charge-discharge tests of these films were conducted and compared. The different electrochemical characteristics of these films were attributed to the modified crystallography, morphology, and thermal stress. The LiCoO₂ film deposited at 400 °C showed a well-defined 4.0 V voltage plateau on charge and a 3.9 V plateau on discharge, and delivered 54.5 μAh/cm² μm at the first discharge capacity, with good cycling performance, giving evidence that such films could be used as the thin film cathodes for lithium microbatteries.     

Fabrication and characterization of ITO thin films on heat-resistant transparent flexible clay films

Transparent conductive indium tin oxide (ITO) thin films were deposited on transparent flexible clay films with heat resistant and high gas barrier properties by rf magnetron sputtering. The electrical, structural, and optical properties of these films were examined as a function of deposition temperature. A lowest resistivity of 4.2 × 10^− 4 Ωcm and an average transmittance more than 90% in the visible region were obtained for the ITO thin films fabricated at deposition temperatures more than 300 °C. It was found that ITO thin films with low resistivity and high transparency can be achieved on transparent flexible clay film using conventional rf magnetron sputtering at high temperature, those characteristics are comparable to those of ITO thin films deposited on a glass substrate.     

Influence of air oxidation on the properties of decorative NbOxNy coatings prepared by reactive gas pulsing

In this work the oxidation resistance of DC reactive sputtered niobium oxynitrides and its influence on the properties of the films are studied. The depositions have been carried out by DC magnetron sputtering with a reactive gas pulsing process. The nitrogen flow was kept constant and the oxygen flow was pulsed. Pulse durations of 10 s produced multilayer coatings with a period of λ = 10 nm. Three sets of films with increasing duty cycle (= on-time of high oxygen flow / pulse duration) have been deposited. The films were subsequently annealed in air at 400, 500 and 600 °C, respectively.X-ray diffraction measurements showed a clear and progressive change from a roughly amorphous nature of the films to a crystalline oxide-type compound for those annealed at 600 °C, which was consistent with the composition analysis. For annealing temperatures of 500 and 600 °C, the coatings presented a significant reduction in hardness, approaching the values characteristic of Nb₂O₅-type films. Moreover, the residual stress measurements performed by using the deflection method revealed low values in all the coatings nearly independent on the annealing temperature.Color variation in the CIE − L^?a^?b^? color space and the reflectance in the UV-visible spectrum range of these niobium oxynitrides were investigated and correlated to their chemical composition and structural features. For both properties, the variation tendencies are quite similar, showing the transition from a nitride-type alloy to an oxide-type one with increasing annealing temperature.     

Lanthanum silicate thin films for SOFC electrolytes synthesized by magnetron sputtering and subsequent annealing

Thin films of La and Si with Si/(La + Si) atomic ratios ranging from 0.36 to 0.44 were produced by magnetron sputtering in pure Ar. For all compositions, the apatite-like La_9.33Si₆O₂₆ phase was formed during annealing in air at 900 °C. A preferential orientation was developed during annealing of the films with higher silicon content while formation of oxide impurities was detected for the films with less silicon. Silicon segregation to the thin film/substrate interface was observed after annealing for thin films with higher Si/(La + Si) atomic ratios. The higher ionic conductivity values were obtained with the films with lower silicon content (2.81 × 10^− 3 Scm^− 1 at 800 °C for the film with Si/(La + Si) atomic ratio of 0.36). This film presented the lower activation energy E_a (0.94 eV).     

Low temperature growth of nanocrystalline TiO2 films with Ar/O2 low-field helicon plasma

TiO₂ thin films were deposited on silicon wafer substrates by low-field (1 < B < 5 mT) helicon plasma assisted reactive sputtering in a mixture of pure argon and oxygen. The influence of the positive ion density on the substrate and the post-annealing treatment on the films density, refractive index, chemical composition and crystalline structure was analysed by reflectometry, Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD). Amorphous TiO₂ was obtained for ion density on the substrate below 7 × 10¹⁶ m^− 3. Increasing the ion density over 7 × 10¹⁶ m^− 3 led to the formation of nanocrystalline (~ 15 nm) rutile phase TiO₂. The post-annealing treatment of the films in air at 300 °C induced the complete crystallisation of the amorphous films to nanocrystals of anatase (~ 40 nm) while the rutile films shows no significant change meaning that they were already fully crystallised by the plasma process. All these results show an efficient process by low-field helicon plasma sputtering process to fabricate stoichiometric TiO₂ thin films with amorphous or nanocrystalline rutile structure directly from low temperature plasma processing conditions and nanocrystalline anatase structure with a moderate annealing treatment.     

High-repetition rate pulsed laser deposition of ZrC thin films

ZrC thin films were grown on (100) Si substrates by the pulsed laser deposition (PLD) technique using a high-repetition rate excimer laser working at 40 Hz. The substrate temperature during depositions was set at 300 °C and the cooling rate was 5 °C/min. X-ray diffraction investigations showed that the films were crystalline. Films deposited under residual vacuum or 2 × 10^− 3 Pa of CH₄ atmosphere exhibited a (200)-axis texture, while those deposited under 2 × 10^− 2 Pa of CH₄ atmosphere were found to be equiaxed. The surface elemental composition of as-deposited films, analyzed by Auger electron spectroscopy (AES), showed the usual high oxygen contamination of carbides. Once the topmost − 3-5 nm region was removed, the oxygen concentration rapidly decreased, being around 3-4% only in bulk. Scanning electron microscopy (SEM) investigations showed a smooth, featureless surface morphology, corroborating the roughness values below 1 nm (rms) obtained from simulations of the X-ray reflectivity (XRR) curves. From the same simulations we also estimated films mass density values of around 6.32-6.57 g/cm³ and thicknesses that correspond to a deposition rate of around 8.25 nm/min. Nanoindentation results showed a hardness of 27.6 GPa and a reduced modulus of 228 GPa for the best quality ZrC films deposited under an atmosphere of 2 × 10^− 3 Pa CH₄.     

Structural, optical and electrical properties of N-doped ZnO thin films prepared by thermal oxidation of pulsed filtered cathodic vacuum arc deposited ZnxNy films

In this study, N-doped ZnO thin films were fabricated by oxidation of Zn_xN_y films. The Zn_xN_y thin films were deposited on glass substrates by pulsed filtered cathodic vacuum arc deposition (PFCVAD) using metallic zinc wire (99.999%) as a cathode target in pure nitrogen plasma. The influence of oxidation temperature, on the electrical, structural and optical properties of N-doped ZnO films was investigated. P-type conduction was achieved for the N-doped ZnO obtained at 450 °C by oxidation of Zn_xN_y, with a resistivity of 16.1 Ω cm, hole concentration of 2.03 × 10¹⁶ cm⁻³ and Hall mobility of 19 cm²/V s. X-ray photoelectron spectroscopy (XPS) analysis confirmed the incorporation of N into the ZnO films. X-ray diffraction (XRD) pattern showed that the films as-deposited and oxidized at 350 °C were amorphous. However, the oxidized films in air atmosphere at 450-550 °C were polycrystalline without preferential orientation. In room temperature photoluminescence (PL) spectra, an ultraviolet (UV) peak was seen for all the samples. In addition, a broad deep level emission was observed.     

Effects of sputtering pressure and post-metallization annealing on the physical properties of rf-sputtered Y2O3 films

Y₂O₃ thin films were prepared by rf-sputtering under various sputtering pressures at room temperature. Spectroscopic ellipsometer, X-ray diffraction and semiconductor parameter analyzer were used to characterize the studied films. The results show the crystallinity and leakage current density of the films improved with decreasing sputtering pressure. The effects of post-metallization annealing (PMA) on optical, structural and electrical properties of the films were also evaluated. It is found that PMA can significantly enhance the electrical performance of Y₂O₃ film, and the lowest leakage current is found to be 1.54 × 10⁻⁸ A/cm² at 1 MV/cm for the samples treated at 350 °C for 30 min. The leakage current mechanisms were discussed as well, which reveals that space charge limited current dominates the as-deposited films while Schottky mechanism describes the PMA treated ones well.     

Conductive and transparent Bi-doped ZnO thin films prepared by rf magnetron sputtering

Bi-doped ZnO thin films were grown on glass substrates by ratio frequency (rf) magnetron sputtering technique and followed by annealing at 400 °C for 4 h in vacuum (~ 10^− 1 Pa). The effect of argon pressure on the structural, optical, and electrical properties of the Bi-doped films were investigated. The XRD patterns show that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. Some excellent properties, such as high transmittance (about 85%) in visible region, low resistivity value of 1.89 × 10^− 3 W cm and high carrier density of 3.45 × 10²⁰ cm^− 3 were obtained for the film deposited at the argon pressure of 2.0 Pa. The optical band gap of the films was found to increase from 3.08 to 3.29 eV as deposition pressure increased from 1 to 3 Pa. The effects of post-annealing treatments had been considered. In spite of its low conductivity comparing with other TCOs, Bi-doping didn't appreciably affect the optical transparency in the visible range of ZnO thin films.     

Erosion-oxidation behaviour of pack-aluminized 9% chromium steel under fluidized-bed conditions at elevated temperature

Pack-aluminized 9% chromium steel specimens were exposed to angular silica sand particles in a fluidized-bed erosion-oxidation rig for 200 h. The exposures were conducted in air at temperatures of 550 °C to 700 °C for particle impact angles of 30° and 90°, at speeds of 7.0-9.2 m s⁻¹. Subsequently, the mean thickness changes of the specimens were determined and the specimens were examined and analyzed by scanning electron microscopy and X-ray diffraction. The specimens experience only slight thickness changes for 30° angle impacts but significant material loss for 90° angle impacts, typical of a brittle erosion process. Under 30° angle impacts, the coatings were mostly retained on the substrate surface and slightly deformed. Thin oxide scales were detected on the surface at all test temperatures. Under 90° angle impacts, thickness losses increased with increase in speed and temperature up to 650 °C, resulting in complete loss of the coating in the test period. A porous, cracked, but continuous, oxide scale was observed on the surface of the exposed substrate. At 700 °C, the coating was partially retained on the substrate, with the residual coating thickness decreasing with increase in speed. Explanations for these observations are presented, the interactions between the erosion and oxidation processes for the specimens are discussed and the degradation mechanisms for the coatings under the test conditions are described in this paper.     

Effect of thermal annealing on the corrosion protection of stainless steel by poly(3-octyl thiophene)

Poly(3-octyl thiophene) (P3OT) coatings have been chemically deposited by drop casting onto 304-type stainless steel. P3OT films were thermally annealed at 55, 80 and 100 °C in air during 30 h and their corrosion resistance was estimated by using polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy measurements, EIS. P3OT films decreased the corrosion rate of the substrate by at least one order of magnitude, although the best corrosion protection was given by annealing it at 100 °C whereas the worst corrosion protection was given by annealing the coating at 80 °C.