Influence of processing variables on the structure and properties of ZnO films (original) (raw)
Related papers
Materials Letters, 2002
Thin films of zinc oxide (ZnO) have been deposited onto glass substrates using a simple and inexpensive spray pyrolysis technique. A nonaqueous methanolic solution of zinc acetate was used as a spraying solution. The concentration of the solution was varied between 0.025 to 0.4 M. The films prepared at different solution concentrations were uniform and well adherent to the substrates. X-ray diffraction (XRD) studies showed that all the films were polycrystalline having hexagonal wurtzite-type crystal structure with strong orientation along (002) plane except 0.025 M, which exhibits a strong orientation in along (100) plane. The bandgap energy, electrical resistivity and thermoelectric power of the films were found to be dependent on the solution concentration. As solution concentration increases, the bandgap energy attenuates from 3.33 to 3.24 eV. The room temperature electrical resistivity was found to be vary in the range 10 2 to 10 À 3 V cm, whereas thermoelectric power increases from 1 Â 10 À 6 to 8 Â 10 À 5 V/K. All the films showed n-type conductivity as evidenced from thermoelectric power (TEP) measurement.
Materials Science-Poland, 2019
An aqueous colloidal solution was prepared at 80 °C and pH = 9 from suitable chemical compounds to produce zinc oxide (ZnO) crystals and thin films. The ZnO crystals were grown in the colloidal solution under special conditions. Their micrographs showed ZnO rods with hexagonal structure. The number of the rods, increased over time. The ZnO thin films were produced on glass substrates in the same colloidal solution using the chemical bath deposition (CBD) method in different deposition times. The produced films were post-annealed for about one hour at 400 °C. Crystalline structure, phase transitions and nanostructure of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). ZnO wurtzite structure was dominant, and by increasing the deposition time, the films became more crystalline. Nanostructure of the films changed from rod to wire and transformed into pyramid-like structures. Also, morphology of the films chang...
Optical and structural properties of thin films of ZnO at elevated temperature
Zinc oxide (ZnO) thin films were prepared on glass substrate by sol-gel dip-coating method. The paper presents the properties of zinc oxide thin films deposited on soda-lime-glass substrate via dip-coating technique, using zinc acetate dehydrate and ethanol as raw materials. The effect of withdrawal speed on the crystalline structure, surface morphology and optical properties of the thin films has been investigated using XRD, SEM and UV-Vis spectrophotometer. X-ray diffraction study shows that all the films have hexagonal wurtzite structure with preferred orientation in (0 0 2) direction and transmission spectra showed highly transparent films with band gap ranging from 3.78 to 3.48 eV.
Uniform & homogeneous Zinc Oxide thin films (ZnO) were deposited on cleaned glass substrates by spray CVD technique. Zinc acetate dehydrate and methanol were used as a starting material and solvent. The effect of deposition parameters on structural, optical & electrical properties of the ZnO thin films was investigated. Thermogravimetric analysis (TGA) of the Zinc acetate showed that weight loss continued until 330 o C. Structural characterization confirmed polycrystalline nature possessing hexagonal wurtzite structure with crystallite size varying between 100.7 and 268.6 nm. The electrical studies established that the films deposited at 330 o C reveal enhancing electrical conduction in ZnO thin films and beyond that the distortion caused in the lattice causes to lower the conductivity. The optical absorption studies reveal that the transition is direct band gap energy. The films also exhibited distinct changes in their optical properties, including a red shift of bandgap. KEYWORDS:...
In this study, we use dipping and spinning methods to coat glass slides with sol-gel ZnO thin films, composed of zinc acetate dihydrate, monoethanolamine (MEA), de-ionized water and isopropanol. The effect of the annealing temperature on the structural morphology and optical properties of these films is investigated. These ZnO films were preheated at 275 ºC for 10 min and annealed either at 350, 450 or 550 ºC for 60 min. As-deposited films, formed by amorphous zinc oxide-acetate submicron particles, are transformed into a highly-oriented ZnO after thermal treatment. The surface morphology, phase structure and optical properties of the thin films were investigated by scanning electron microscopy, X-ray diffraction (XRD) and optical transmittance. Both techniques produced nanostructured ZnO thin films with well-defined orientation. The annealed films were transparent in the visible range with an absorption edge at about 375 nm and a transmittance of ca 85-90% with an average diameter of 40 nm. XRD results show the film was composed of polycrystalline wurtzite, with a preferential c-axis orientation of (002) and a single sharp XRD peak at 34.40, corresponding to the hexagonal ZnO. The grain size is increased by the annealing temperature. Both coating techniques create sol-gel ZnO films with the potential for application as transparent electrodes in optic and electronic devices.
Substrate induced modifications in the structural and optical properties of zinc oxide thin films
2013
Zinc oxide thin films were grown on two different substrates (quartz and ITO coated glass) using RF sputtering technique. X-ray diffraction study confirms the formation of hexagonal wurtzite phase of the grown films. The optical properties of the thin films studied using UV-Vis spectroscopy technique show no change in the optical band gap of the grown films, however the enhancement in absorption edge is observed for the films grown on ITO coated glass substrate as compared to quartz.
Realization and study of ZnO thin films intended for optoelectronic applications
The objective of this study is the realization of zinc oxide (ZnO) thin films intended for optoelectronic applications. For this purpose, thin films were prepared by spray pyrolysis technique from zinc acetate solutions of different molarities (0.025 M, 0.05 M and 0.1 M) used as precursors on Si and glass substrates heated between 200 and 500 °C. The nozzle to substrate distance was varied between 20 and 30 cm. Structural, optical and electrical properties of the films have been studied. The results indicated that the films deposited were transparent in the visible region, well adherent to the substrates and presented surface roughness. All samples were polycrystalline in nature, having hexagonal würtzite type crystal structure. A (002) preferred orientation was observed at 450°C and a 0.025M molarity. The optical energy gap measured was about 3.3 eV. The refractive index values presented small variations with the deposition conditions and were located between 1.8 and 2.0. The electrical properties showed that the samples are natively n-type semiconductor and the electrical conductivity at room temperature varied between 10-5 and 10 2 (Ω.cm)-1 .
Morphology of zinc oxide thin films deposited by spray pyrolysis
The effect of deposition temperature on the surface morphology and optical properties of zinc oxide (ZnO) thin films were studied. The ZnO films were deposited on microscopic glass substrates using the spray pyrolysis method for different substrate deposition temperatures. The deposited films were characterized by an X-ray diffractometer (XRD), a spectrophotometer, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The transmittance spectra recorded through the spectrophotometer exhibits 85% transmittance. The XRD spectra showed polycrystalline nature of ZnO film. Surface parameters were calculated and compared for different thin films. It showed that the films were polycrystalline with hexagonal wurtzite structure and c-axis was perpendicular to the substrate. The grain size of the films changed from 240 to 440 nm with different substrate temperatures. The optical energy gap of thin films increases from 3.26 eV to 3.35 as the substrate temperature increasing fro...
THE Coatings, 2021
ZnO thin films were synthesized on silicon and glass substrates using the plasma-enhanced chemical vapor deposition (PECVD) technique. Three samples were prepared at substrates temperatures of 200, 300, and 400 °C. The surface chemical composition was analyzed by the use of X-Ray Photoelectron spectroscopy (XPS). Structural and morphological properties were studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties were carried out by UV-visible spectroscopy. XPS spectra showed typical peaks of Zn(2p3/2), Zn(2p1/2), and O(1s) of ZnO with a slight shift attributed to the substrate temperature. XRD analysis revealed hexagonal wurtzite phases with a preferred (002) growth orientation that improved with temperature. Calculation of grain size and dislocation density revealed the crystallization improvement of ZnO when the substrate temperature varied from 200 to 400 °C. SEM images of ZnO films showed textured surfaces composed of grains of spheric...
Study of zinc oxide thin film characteristics
EPJ Web of Conferences
This paper presents the characterization of ZnO thin films with the thickness of 8nm, 30nm, and 200nm. The thin films were prepared using sol-gel method and has been deposited onto different substrate of silicon wafer, glass and quartz. The thin films were annealed at 400, 500 and 600ºC. By using UV-Vis, the optical transmittance measurement were recorded by using a single beam spectrophotometer in the wavelength 250nm to 800nm. However, the transmittance in the visible range is hardly influenced by the film thickness, substrate used and annealed temperature and the averages are all above 80%. On surface morphology observed by AFM and FESEM, the results show that the increase of film thickness and annealed temperature will increase the mean grain size, surface-to-volume ration and RMS roughness. Besides that, higher annealing temperature cause the crystalline quality to gradually improve and the wurtzite structure of ZnO can be seen more clearly. Nonetheless, the substrate used had no effect on surface morphology, yet the uniformity of deposition on silicon wafer is better than glass and quartz.