Zinc oxide thin films by the spray pyrolysis method

Undoped and In-doped ZnO thin films have been prepared on glass substrates from solutions of Zn(CH₃CO₂)₂2H₂O in a mixture of deionized water and isopropyl alcohol by spray pyrolysis. Their optical, morphological and structural qualities have been studied and the effect of the preparation conditions discussed. It was shown that the main factors determining the parameters of ZnO films are the growth temperature and the indium concentration. The growth temperatures of 625–675 K, indium doping levels of 1–1.5 at.% and precursor concentrations of 0.1–0.2 mol 1⁻¹ are preferable to achieve ZnO films with optical and structural qualities as required for solar cell applications.     

Performances presented by zinc oxide thin films deposited by spray pyrolysis

The effect of doping and annealing atmosphere on the performances of zinc oxide thin films prepared by spray pyrolysis have been studied. The results show that the way doping influences the electrical and structural properties depends also on the characteristics of the doping element. Annealing the as-deposited films in an inert atmosphere leads to a substantial reduction in the resistivity of the films deposited and to an increase on the degree of film’s crystallinity.     

Characterization of molybdenum-doped indium oxide thin films by spray pyrolysis technique

In this research, indium oxide nanostructure undoped and doped with Mo were prepared on glass substrates using spray pyrolysis technique. Various parameters such as dopant concentration and deposition temperatures were studied. Structural properties of these films were investigated by X-ray diffraction and scanning electron microscopy. Electrical and optical properties have been studied by Hall effect and UV–Visible spectrophotometer, respectively. The thickness of the films was determined by PUMA software. The variation of refractive index, extension coefficient and bandgap of these films also were investigated.     

Transparent conducting lithium-doped nickel oxide thin films by spray pyrolysis technique

Nickel oxide (NiO) and lithium-doped nickel oxide films were deposited by the spray pyrolysis technique using NiCl2 and LiCl as starting materials. All the films were greenish-grey in colour and confirmed by X-ray analysis. The best NiO films were obtained when the substrate temperature, Ts=480 °C where a conductivity of 2.1×10-1Ω-1 cm-1 and transparency above 80% in the visible region are achieved. High transparency (above 80%) and highly conducting NiO films were obtained when doped with lithium. This revised version was published online in November 2006 with corrections to the Cover Date.     

Growth and characterization of indium oxide thin films prepared by spray pyrolysis

Highly transparent and conducting indium oxide thin films are prepared on glass substrates from precursor solution of indium chloride. These films are characterized by X-ray diffraction, scanning electron microscopy and optical transmission. The preferential orientation of these films is found to be sensitive to deposition parameters. A comparative study has been made on the dependence on the thickness of the film on substrate temperatures with aqueous solution and 1:1 C₂H₅OH and H₂O as precursors. Films deposited at optimum conditions have 167 nm thickness and exhibited a resistivity of 2.94 × 10⁻⁴ Ω m along with transmittance better than 82% at 550 nm. The analytical expressions enabling the derivation of the optical constants of these films from their transmission spectrum only have successfully been applied. Finally, the refractive index dispersion is discussed in terms of the single-oscillator Wemple and Didomenico model.     

Growth and characterization of indium oxide thin films prepared by spray pyrolysis

Highly transparent and conducting indium oxide thin films are prepared on glass substrates from precursor solution of indium chloride. These films are characterized by X-ray diffraction, scanning electron microscopy and optical transmission. The preferential orientation of these films is found to be sensitive to deposition parameters. A comparative study has been made on the dependence on the thickness of the film on substrate temperatures with aqueous solution and 1:1 C₂H₅OH and H₂O as precursors. Films deposited at optimum conditions have 167 nm thickness and exhibited a resistivity of 2.94 × 10⁻⁴ Ω m along with transmittance better than 82% at 550 nm. The analytical expressions enabling the derivation of the optical constants of these films from their transmission spectrum only have successfully been applied. Finally, the refractive index dispersion is discussed in terms of the single-oscillator Wemple and Didomenico model.     

Nanocrystalline copper selenide thin films by chemical spray pyrolysis

Thin films of copper selenide were deposited onto amorphous glass substrates at various substrate temperatures by computerized spray pyrolysis technique. The as deposited copper selenide thin films were used to study a wide range of characteristics including structural, surface morphological, optical and electrical, Hall Effect and thermo-electrical properties. X-ray diffraction study reveals that the films are polycrystalline in nature with hexagonal (mineral klockmannite) crystal structure irrespective of the substrate temperature. The crystalline size is found to be in the range of 23–28 nm. The SEM study reveals that the grains are uniform with uneven spherically shaped and spread over the entire surface of the substrates. EDAX analysis confirmed the nearly stoichiometric deposition of the film at 350 °C. The direct band gap values are found to be in the range 2.29–2.36 eV depending on the substrate temperature. The Hall Effect study reveals that the films exhibit p-type conductivity. The values of carrier concentration and mobility for the film are found to be 5.02 × 10¹⁷ cm^?3 and 5.19 × 10^?3 cm² V^?1 s^?1; respectively for film deposited at 350 °C.     

Growth of thin ZnO films by ultrasonic spray pyrolysis

We report the growth of high-quality thin ZnO films with controlled microstructure on Si(111) substrates by ultrasonic spray pyrolysis of Zn-containing solutions.     

Ag diffusion in ZnS thin films prepared by spray pyrolysis

ZnS thin films were deposited by spray pyrolysis method on glass substrates. Diffusion of Ag in ZnS thin films was performed in the temperature range 80-400 °C under a nitrogen atmosphere. The diffusion of Ag is determined with XRF, and the obtained concentration profile allows to calculate the diffusion coefficient. The temperature dependence of Ag diffusion coefficient is determined by the equation D = 8 × 10^− 9 exp(− 0.10 eV / kT). It was found that the as-grown undoped high resistive n-type ZnS thin films were converted to the p-type upon Ag doping with a slight increase in resistivity only by rapid thermal annealing at 400 °C in N₂ atmosphere. In addition, the band gap of the p-type film was decreased as compared with the undoped sample annealed under the same conditions. The results were attributed to the migration of Ag atoms in polycrystalline ZnS films by means of both along intergrain surfaces and intragrain accompanied by interaction with native point defect.     

Optical constants of CdS thin films prepared by spray pyrolysis

CdS thin films were prepared by spray pyrolysis techniques. Variable angle spectroscopic ellipsometry was used for optical constant calculations. Multiple angle measurements were taken in the most sensitive angle of incidence region. The sensitive regions of angle of incidence were obtained theoretically using 3-dimensional graph ofδψ andδΔ. Real partn and imaginary partk of the complex refractive index of the samples were calculated in the wavelength range 470–650 nm, taking into account surface roughness. Bruggeman’s effective medium approximation is used for analysis of the surface rough layer of the thin films.     

喷雾热分解法制备SnO2·F薄膜与导电性能研究

以SnCl4·5H2O和NH4F为原料,采用喷雾热分解的方法在片状日用玻璃基材和石英玻璃基材上制得了掺氟氧化锡透明导电薄膜.采用X射线衍射仪(XRD)和扫描电镜(SEM)分别对薄膜的内部结构和表面形貌进行了表征.研究了F-的掺杂量、喷涂温度、沉积时间和热处理对薄膜方阻R□的影响.实验结果表明,当[NH4F]/[SnCl4·5H2O]=32wt%、成膜温度为450℃、喷涂时间为15s时,可使所得薄膜的方阻R□达最低,为10Ω/□.     

Perovskite-type lanthanum chromium-based oxide films prepared by ultrasonic spray pyrolysis

Ultrasonic spray pyrolysis was used to form 2–8 m thick LaCrO₃ films on different substrates from La(CrO₄)(NO₃)·nH₂O precursor films. There was an optimum substrate temperature for the formation of uniform precursor films by the spray pyrolysis. When the substrate temperature was lower than 250 °C, dry precursor films were not formed, while above 250 °C the deposition rate decreased with substrate temperature. The precursor films were converted to perovskite-type oxide films by heat treatment at 800 °C in a nitrogen atmosphere. Both A-site substituted (La_0.8Ca_0.2) CrO₃ and B-site substituted La(Cr_0.5Mn_0.5)O₃ oxide films were formed in a similar manner. Electronic conductivity of the oxide films was improved by repetitions of the spray pyrolysis and heat treatment in nitrogen.     

Influence of the doping and annealing atmosphere on zinc oxide thin films deposited by spray pyrolysis

Undoped and doped (indium and aluminium) zinc oxide (ZnO) thin films have been prepared by spray pyrolysis, and the effect of the doping and annealing atmosphere on the electrical, optical and structural properties of the produced films has been investigated. The deposited films have a high resistivity. Annealing the films in an argon atmosphere or under vacuum leads to a substantial reduction of the electrical resistivity of the films and to an increase on the degree of cristallinity of the deposited material. The most pronounced changes were observed in the films annealed in Argon. The results also indicate that doping highly influences the electrical and structural properties of the films, which is more pronounced in the films doped with Indium.     

Synthesis and characterization of nanostructured nickel oxide thin films prepared with chemical spray pyrolysis

Nickel oxide thin films have been deposited in an open atmosphere onto glass substrates by chemical spray pyrolysis using aqueous nickel acetate solutions and air as driving gas. The films show a strong variation in the surface morphology depending on the substrate temperature and the precursor solution flux. At 350 °C substrate temperature, a reticular tissue-like film morphology is obtained, becoming the reticular nickel oxide fibres of the film thicker with increasing precursor solution flux. At 450 °C substrate temperature, the film growth rate is 4 times slower and a highly symmetric self-ordering of the material at nanometer length scale occurs. These films consist of interconnected grains separated by pores, both of about 100 nm in size. XRD and TEM revealed that the films are cubic NiO, being the crystallite size around 10 nm. The optical band gap of the films decreases strongly for increasing film thickness from 4.3 eV to 3.65 eV.     

Characterization of FeS2-pyrite thin films synthesized by sulphuration of amorphous iron oxide films pre-deposited by spray pyrolysis

FeS₂-thin films with good crystallinity were synthesized by a simple method which consists of sulphuration, under vacuum, of amorphous iron oxide thin films pre-deposited by spray pyrolysis of FeCl₃·6H₂O (0.03 M)-based aqueous solution onto glass substrates heated at 350 °C. At optimum sulphuration temperature (450 °C) and duration (6 h), black green layers having granular structure and high absorption coefficient (5.10⁴ cm⁻¹) were obtained. The study of the electrical properties of the as-prepared films vs. the temperature variations showed three temperature domain dependence of the conductivity behaviour. The first one corresponds to the high temperature range (330 K–550 K) for which an Arrhenius plot type was obtained. The activation energy value was estimated at about 61.47 meV. The second domain corresponding to the intermediate temperature range (80 K–330 K) showed a variable activation energy between the grain boundaries. The barrier height, q¯, was estimated to 27±0.5 meV, and the standard deviation, qσ, was evaluated at about 14±0.5 meV. We found that at lower temperatures (20 K–80 K), the conductivity is governed by two conduction types. The density of localised states, was about 2.45×10²⁰ eV⁻¹ cm⁻³.     

Gas sensitivity of metal oxide mixed tin oxide films prepared by spray pyrolysis

Various kinds of SnO₂ films, modified with the addition of iron, antimony, copper, titanium, manganese, nickel, cobalt or calcium oxides, were fabricated by using the spray pyrolysis technique and their gas-sensing characteristics were studied. From electrical measurements in air, the relative sensitivity towards inflammable gas of these SnO₂-based film sensors was compared. It was observed that SnO₂-based films of higher electrical resistance had a tendency to have higher sensitivity towards ethanol than the SnO₂-based films of lower resistance. The addition of p-type metal oxides, such as NiO and MnO, to the SnO₂ matrix was found to be effective in increasing the sensitivity towards inflammable gas.     

Highly transparent and conducting indium-doped zinc oxide films by spray pyrolysis

Spray pyrolysis has been used to deposit highly transparent and conducting films of indium-doped zinc oxide. The roles of various deposition parameters have been investigated and the optimum deposition conditions have been outlined. Without any post-deposition heat treatment, as-deposited films with a resistivity of about $\text{(8 ? 9) × 10}{}^{-4}\text{Ω}\text{cm}$ and an average visible transmittance of about 85% have been obtained. The structural, electrical and optical properties have been studied. The electron transport properties suggest that the films are degenerate and the mobility data can be understood in terms of a grain boundary trapping model.     

High quality-low temperature aluminum oxide films deposited by ultrasonic spray pyrolysis

High quality aluminum oxide thin films have been prepared at relatively low substrate temperatures using aluminum acetylacetonate as source material. The structural properties were analyzed by ellipsometry and infrared spectroscopy. The electrical integrity was analyzed by I–V and C–V measurements performed in metal/oxide/semiconductor structures where the deposited oxides were incorporated. Good quality aluminum oxide films were obtained at substrate temperatures as low as 350 °C. The deposition rate has relatively high values from 7.0 to 11.4 nm/min. The refractive index takes values around 1.645, which is of the order of those obtained using vacuum processes. Destructive breakdown electric field is higher than 6 MV/cm. The capture cross section per unit area (9.3×10^-15cm²) is associated with trapping centers with coulombic potential. From quasistatic and high frequency C–V measurements, a density of interface states at midgap of 1.6×10¹¹ (eVcm²)^-1 was calculated.     

Comparative study of ITO and FTO thin films grown by spray pyrolysis

Tin doped indium oxide (ITO) and fluorine doped tin oxide (FTO) thin films have been prepared by one step spray pyrolysis. Both film types grown at 400 °C present a single phase, ITO has cubic structure and preferred orientation (4 0 0) while FTO exhibits a tetragonal structure. Scanning electron micrographs showed homogeneous surfaces with average grain size around 257 and 190 nm for ITO and FTO respectively.The optical properties have been studied in several ITO and FTO samples by transmittance and reflectance measurements. The transmittance in the visible zone is higher in ITO than in FTO layers with a comparable thickness, while the reflectance in the infrared zone is higher in FTO in comparison with ITO. The best electrical resistivity values, deduced from optical measurements, were 8 × 10⁻⁴ and 6 × 10⁻⁴ Ω cm for ITO (6% of Sn) and FTO (2.5% of F) respectively. The figure of merit reached a maximum value of 2.15 × 10⁻³ Ω⁻¹ for ITO higher than 0.55 × 10⁻³ Ω⁻¹ for FTO.