On the effect of acetic acid on physical properties of chemically sprayed fluorine-doped ZnO thin films

Fluorine-doped zinc oxide (ZnO:F) thin films onto sodocalcic glass substrates, starting from a highly concentrated starting solution (0.4 M) containing zinc acetate and hydrofluoric acid diluted in a mixture of deionized water, acetic acid , and methanol, using the chemical spray deposition technique, were deposited and characterized. The effect of the acetic acid content in the starting solution, and the substrate temperature on the electrical resistivity, structure, morphology and optical characteristics was studied. The samples were polycrystalline in nature, but as the acetic acid content in the starting solution increases, the preferential orientation shows a switching from (002) to (101). For a predetermined deposition temperature, as the acetic acid content increases, the film resistivity values show an increase. The minimum resistivity in the order of 6 × 10^− 3 Ω cm was found for the films deposited with the lowest acetic acid content used. The surface morphology varies from agglomerated grains to rod-like shaped grains as a function of the acetic acid content.     

Effect of solvent ratio on the properties of highly oriented sprayed fluorine-doped tin oxide thin films

Transparent conducting thin films of F:SnO₂ have been deposited onto preheated glass substrates by a spray pyrolysis technique using pentahydrate stannic chloride (SnCl₄·5H₂O) and ammonium fluoride (NH₄F) as precursors and mixture of water and propane-2-ol as solvent. The concentration of SnCl₄·5H₂O and NH₄F is kept fixed and the ratio of water and propane-2-ol solvent in the spraying solution is varied. A fine spray of the source solution using air as a carrier gas has grown films of thickness up to 995 nm. Optical absorption, X-ray diffraction, Van der Pauw technique for measurement of a sheet resistance and Hall effect measurements at room temperature for determination of carrier density and conductivity have been used. The as-deposited films are of polycrystalline SnO₂ with a tetragonal crystal structure and are preferentially having orientation along the (200) direction with texture coefficient as high as 6.16. The average grain size for the as-deposited sample is found to be of the order of 44 nm. The films have moderate optical transmission (up to 70–85% at 550 nm). The figure of merit (ϕ) values vary from 1.95 · 10^− 3 to 35.68 · 10^− 3 Ω^− 1. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) for the optimized sample is 5.1 Ω. The films have a resistivity of 5.43 · 10^− 4 Ω cm and mobility around 7.38 cm² V^− 1 s^− 1.     

Magnesium-doped zinc oxide electrochemically grown on fluorine-doped tin oxide substrate

Nanostructures of magnesium (Mg) doped Zinc oxide (ZnO) were successfully deposited on conducting fluorine-doped tin oxide (FTO) coated glass plates by cathodic electrochemical deposition method at different potentials and temperature conditions. The deposited samples were characterized by XRD and SEM techniques to confirm their structures, morphologies and optical properties. These measurements show that Mg doped ZnO has a wurtzite structure and that the strongest intensity of the (002) peak is found at 60 degrees C and -1.0 V. Tunable transmittance of Mg doped ZnO has a band gap energy from 3.45 eV to 3.82 eV, which is the direct evidence of doping.     

Effect of substrate temperature on the properties of pyrolytically deposited nitrogen-doped zinc oxide thin films

The effect of substrate temperature (T_s) on the properties of pyrolytically deposited nitrogen (N) doped zinc oxide (ZnO) thin films was investigated. The T_s was varied from 300 °C to 500 °C, with a step of 50 °C. The positive sign of Hall coefficient confirmed the p-type conductivity in the films deposited at 450 °C and 500 °C. X-ray diffraction studies confirmed the ZnO structure with a dominant peak from (1 0 0) crystal plane, irrespective of the variation in T_s. The presence of N in the ZnO structure was evidenced through X-ray photoelectron spectroscopy (XPS) analysis. The obtained high N concentration reveals that the 450 °C is the optimal T_s. Atomic force microscope (AFM) analysis showed that the surface roughness was increased with the increasing T_s until 400 °C but then decreased. It is found that the transmittance of the deposited films is increased with the increasing T_s. The optical band gap calculated from the absorption edge showed that the films deposited with T_s of 300 °C and 350 °C possess higher values than those deposited at higher T_s.     

Influence of deposition temperature on the properties of sprayed CuInS2 thin films

Copper indium disulfide films were deposited by chemical spray pyrolysis technique at different deposition temperatures. Deposition temperature was explored to understand how it affects the crystallography, stoichiometry, morphology, optical and electrical properties of the deposited films. The chemical composition of the films evaluated by energy dispersive X-ray spectroscopy revealed the presence of copper, indium and sulfur elements in the films. Also it was observed that films formed at higher temperatures are copper rich and also showed deficiency of sulfur. X-ray diffraction patterns showed that the sprayed CuInS₂ films are polycrystalline with chalcopyrite structure and preferred orientation in the (112) direction. Atomic force microscope studies revealed significant variations in the surface morphology of the prepared films with different deposition temperature. An increase in the energy band gap was observed with increasing the deposition temperatures. The temperatures dependence of conductivity of CuInS₂ thin films, determined in the temperature range of 225–400?K, showed their semiconducting behavior.     

Influence of concentration and annealing temperature on spin-coated metal oxide thin films for optoelectronic devices

Journal of Materials Science: Materials in Electronics - The metal oxide thin films, such as cadmium oxide (CdO) and zinc oxide (ZnO) thin films, were deposited by sol–gel-derived spin...     

Peculiarities of nitrogen dioxide detection with sprayed undoped and indium-doped zinc oxide thin films

Nitrogen dioxide (NO₂) sensors based on sprayed zinc oxide (ZnO) thin films have been prepared. The effect of the film thickness and the In-doping on the sensor performance (sensor response and resistance) is analyzed. By adding 3 wt.% of indium nitrate to the spraying solution it is possible to enhance the film-gas response to 5 ppm of NO₂ at 275 °C. At the same time the film resistance is sensibly reduced. The film crystallographic structure, morphology and additive content are studied by means of X-ray Diffraction, Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. The possible sensitization mechanism is discussed.     

The influence of substrate temperature on the properties of aluminum-doped zinc oxide thin films deposited by DC magnetron sputtering

Transparent, conducting, aluminum-doped zinc oxide (AZO) thin films were deposited on Corning 1737 glass by a DC magnetron sputter. The structural, electrical, and optical properties of the films, deposited using various substrate temperatures, were investigated. The AZO thin films were fabricated with an AZO ceramic target (Al₂O₃:2 wt%). The obtained films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The lowest resistivity was 6.0 × 10⁻⁴Ω cm, with a carrier concentration of 2.7 × 10²⁰ cm⁻³ and a Hall mobility of 20.4 cm²/Vs. The average transmittance in the visible range was above 90%.     

Effects of substrate material and annealing temperature on morphology of zinc oxide films

Abstract

A two stage chemical deposition (TSCD) technique is used to produce ZnO films on quartz glass (QG), soda lime glass (SLG) and high purity alumina (HPA) from an aqueous solution of zinc complex. The effects of the substrate material on the chemical composition and morphology of the deposited layer are investigated. The effects of different annealing temperatures (180, 300, 500 and 800°C) on the morphology and orientation of the ZnO crystallites are also determined. X-ray diffraction diffractograms show that above 300°C, the intensity of (002) peak considerably decreases with increasing temperature. Results indicate that changing the substrate from QG to SLG does not significantly influence the chemical composition of the deposited layer. These variations can be attributed to different factors including (a) physorption of cold complex solution, (b) growth behaviour of the nuclei forming on the substrate and (c) the surface energy of the substrate. Owing to the existence of the morphological differences bound to the molecular nature of the substrate, properties of the coatings are found not to be the same. HPA substrate causes clustering of the ZnO crystallites, while QG and SLG substrates do not distinguishably show this effect. Observations show that clustering is intensified by annealing at temperatures > 180°C.     

Influence of annealing temperature on structural,electrical and optical properties of undoped zinc oxide thin films

The undoped zinc oxide thin films were grown on quartz substrate at a substrate temperature of 750 °C by radio frequency magnetron sputtering and post annealed at different temperatures (600–800 °C) for a period of 30 min. The influence of annealing temperature on the structure, electrical and optical properties of undoped ZnO thin films was investigated by X-ray diffraction, Hall-effect, photoluminescence and optical transmission measurements. Results indicated that the electrical properties of the thin films were extremely sensitive to the annealing temperature and the conduction type could be changed dramatically from n-type to p-type, and finally changed to weak p-type when the temperature increased from 600 to 800 °C. Electrical and photoluminescence results indicate that native defects, such as oxygen and zinc vacancies, could play an important role in determining the conductivity of these nominally undoped ZnO thin films. The conversion of the conduction type was attributed to the competition between Zn vacancy acceptor and oxygen vacancy and interstitial Zn donors. At an intermediate annealing temperature of 750 °C, the film behaves the best p-type characteristic, which has the lowest resistivity of 12 Ωcm, hall mobility of 2.0 cm²/V s and carrier concentration of 1.5 × 10¹⁷ cm^?3. The photoluminescence results indicated that the Zn vacancy might be responsible for the intrinsic better p-type characteristic in ZnO thin films.     

Thickness-dependent properties of sprayed iridium oxide thin films

Iridium oxide thin films with variable thickness were deposited by spray pyrolysis technique (SPT), onto the amorphous glass substrates kept at 350 °C. The volume of iridium chloride solution was varied to obtain iridium oxide thin films with thickness ranging from 700 to 2250 Å. The effect of film thickness on structural and electrical properties was studied. The X-ray diffraction (XRD) studies revealed that the as-deposited samples were amorphous and those annealed at 600 °C for 3 h in milieu of air were polycrystalline IrO₂. The crystallinity of Ir-oxide films ameliorate with film thickness thereby preferred orientation along (1 1 0) remains unchanged. The infrared spectroscopic results show Ir–O and Ir–O₂ bands. The room temperature electrical resistivity (ρ_RT) of these films decreases with increase in film thickness. The p-type semiconductor to metallic transition was observed at 600 °C.     

Influence of substrate temperature on phase formation in Al-Cr thin films

Thin films (of the order of nm) of Al-Cr alloys were prepared by successive depositions by an electron gun in a vacuum chamber. Three Al and two Cr layers, of thicknesses as to yield the final composition, were deposited on both hot (350 °C and 440 °C) and cold (70 °C and 108 °C) substrates and the phases formed were characterized in each case by X-ray diffraction and TEM observations, both in bright and in dark field conditions. The results show that on the hot substrates, Bragg peaks that do not correspond to any reported crystalline or quasi-crystalline phase appear. Both the samples on cold substrates and those heated afterwards showed an amorphous structure by X-ray diffractomery but TEM demonstrated the presence of tiny faulted crystallites, with the same Bragg reflections than those deposited on hot substrates. The results show that, for the composition range studied, a new phase not reported before appears and the substrate temperature only produces crystallite growth, not the formation of new phases. Received: 26 May 2000 / Reviewed and accepted: 31 May 2000     

Characterization of aluminum-doped zinc oxide thin films by RF magnetron sputtering at different substrate temperature and sputtering power

In this study, transparent conductive Al doped zinc oxide (ZnO: Al, AZO) thin films with a thickness of 40 nm were prepared on the Corning glass substrate by radio frequency magnetron sputtering. The properties of the AZO thin films are investigated at different substrate temperatures (from 27 to 150 °C) and sputtering power (from 150 to 250 W). The structural, optical and electrical properties of the AZO thin films were investigated. The optical transmittance of about 78 % (at 415 nm)–92.5 % (at 630 nm) in the visible range and the electrical resistivity of 7 × 10^?4 Ω-cm (175.2 Ω/sq) were obtained at sputtering power of 250 W and substrate temperature of 70 °C. The observed property of the AZO thin films is suitable for transparent conductive electrode applications.     

Influence of the substrate temperature on the properties of MoSi2 thin films

Investigations of the microcrystalline structure of sputtered MoSi₂ thin films deposited at temperatures in the range 60–500 °C are described. At low temperatures the films are amorphous, and in the higher range of temperature hexagonal MoSi₂ is detected. Annealing the films at 960 °C to form the low resistivity tetragonal MoSi₂ phase results in different grain sizes depending on the substrate temperature during deposition.     

Electrical, structural and optical properties of fluorine-doped zinc oxide thin films: Effect of the solution aging time

In this paper ageing effects of the solution used to prepare fluorine-doped ZnO films by the spray pyrolysis technique were investigated, concerning its role on the structure, the electrical and optical properties of films produced. The data reveal that the sheet resistance of the ZnO:F thin film decreases with the age of the solution used, reaching a minimum of 24 Ω/□, after 15 days. On the other hand the optical transmittance increases for films deposited using 6 days aging solution, decreasing afterwards as the aging time increases, being the optical transmittance in the visible range below 55%, for films deposited from solutions 36 days in age. The X-ray diffraction spectra show that the aged films are polycrystalline in nature with a [100] predominant orientation. The data also show that the intensity of (100) peak increases as the time of solution age increases, which is related to an improvement of the film crystallinity.     

Effect of substrate temperature and precursor ratio on properties of thin ZnS films sprayed by improved method

Zinc sulphide (ZnS) thin films were prepared by improved spray pyrolysis (ISP) method. The ISP parameters, such as carrier gas flow rate, solution flow rate and substrate temperature, were controlled with an accuracy of ±0.25 lpm, ±1 ml/h and ±1 °C, respectively. The solution was sprayed in a pulsed mode. The substrate temperature was optimized by analyzing substrate temperature dependent properties of thin films. The thin film deposited at a temperature of 450 °C was dense and fairly smooth with satisfactory crystallinity and very small impurity content. The effect of precursor ratio in the solution on structural, compositional and optical properties of thin ZnS films, deposited at a temperature of 450 °C, was studied. A gradual increase in band gap energy from 3.524 eV to 3.634 eV, refractive index from 2.5 to 2.9 and dielectric constant from 6.6 to 8.7 were observed with the variation of solution precursor (Zn:S) ratio from (1:2) to (1:6). The structural and compositional studies support this kind of enhancement in optical properties. The results show that the thin ZnS film prepared by ISP at the substrate temperature of 450 °C from a solution with specific precursor ratio can be used for optoelectronic and photovoltaic applications.     

Low-temperature deposited Titanium-doped zinc oxide thin films on the flexible PET substrate by DC magnetron sputtering

Transparent conducting Titanium-doped zinc oxide thin films (TZO) with high transparency and relatively low resistivity were firstly deposited on water-cooled polyethylene terephthalate (PET) substrates at room temperature by DC magnetron sputtering. The microstructure, optical and electrical properties of the deposited films were investigated and discussed. The XRD patterns show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The electrical resistivity decreases when the sputtering power increases from 45 W to 60 W. However, as the puttering power continue increases from 60 W to 90 W, the electrical resistivity increases rapidly. When the puttering power is 60 W, the films deposited on PET substrate have the lowest resistivity of 4.72 × 10⁻⁴ Ω cm and a relatively high transmittance of above 92% in the visible range.     

Low-temperature deposited Titanium-doped zinc oxide thin films on the flexible PET substrate by DC magnetron sputtering

Transparent conducting Titanium-doped zinc oxide thin films (TZO) with high transparency and relatively low resistivity were firstly deposited on water-cooled polyethylene terephthalate (PET) substrates at room temperature by DC magnetron sputtering. The microstructure, optical and electrical properties of the deposited films were investigated and discussed. The XRD patterns show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The electrical resistivity decreases when the sputtering power increases from 45 W to 60 W. However, as the puttering power continue increases from 60 W to 90 W, the electrical resistivity increases rapidly. When the puttering power is 60 W, the films deposited on PET substrate have the lowest resistivity of 4.72 × 10⁻⁴ Ω cm and a relatively high transmittance of above 92% in the visible range.     

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.