Influence of annealing temperature on the formation and characteristics of sol-gel prepared ZnO films

Abstract

ZnO thin films have been obtained by the sol-gel method from a Zn(OOCCH3)2 precursor on soda lime glass and silicon wafer substrates. The films, obtained by a single dipping procedure, were characterized by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopies, atomic force microscopy, x-ray diffraction and ellipsometry measurements. Thermally untreated and annealed (100–450 °C) films were studied in order to analyze the influence of temperature on the formation and properties of the ZnO coatings. Remarkably, these results indicate that ZnO forms at considerably lower temperatures than 450 °C, which is usually considered in the literature as a reference temperature for the formation of ZnO. Thus, a sharp absorption edge of ZnO at ∼380 nm can be easily observed in the UV-vis spectra of films annealed at 200 and 300 °C, accordingly, and the FTIR data indicate the absence of organic groups at these temperatures. The atomic force microscopy results show a uniform, void-free surface of the films, as well as larger grain sizes as the annealing temperature is increased. The x-ray diffraction patterns show that the films are polycrystalline and also show evidence of the formation of ZnO at temperatures as low as 200 °C. The refractive index values, obtained by ellipsometry, increase with annealing temperature, up to a value of 1.96 for the film fired at 450 °C.

Percolation Mechanism and Characterization of (CdO)y(ZnO)1-y Thin Films

“…The spectrum of the film with X = 0 corresponds to that expected for a film of pure ZnO, with a sharp absorption edge that indicates the presence of a direct bandgap. [10] It can also be observed that there is a shift of the absorption edge towards longer wavelengths, as well as a loss of absorption edge sharpness, as the Cd content in the film increases. This can be ascribed to the contribution of both the direct and indirect CdO bandgaps.…”

“…The procedures employed for the preparation of the ZnO±CdO films were based on those we have previously reported for the preparation of pure ZnO [10] and CdO [11] thin films, where we used novel precursor solutions and worked in basic pH conditions, as compared to the synthetic routes reported by other groups.…”

“…95 % over the 600±1100 nm wavelength range. [11] We present in this work the results of the sol±gel preparation and characterization of homogeneous mixtures of CdO±ZnO thin films (whose preparation was based on the methods used for making ZnO and CdO thin films [10,11] ), with low values of X (X = Cd/(Cd + Zn), i.e., the atomic ratio in solution), from X = 0 to 0.32, in DX = 0.04 steps.…”

PROPERTIES OF ZnO:AL THIN FILMS, OBTAINED BY THE SOL-GEL METHOD

“…The procedure to prepare stable ZnO:Al precursor solutions was very similar to that recently reported by the authors [5]. The doping source was A1(N0 3 )3*9H 2 0, dissolved in methanol (50:1 solvent:solute molar ratio); the dopant solution was added to the precursor solution before the addition of triethylamine [5].…”

Ultraviolet Luminescent, High‐Effective‐Work‐Function LaTiO3‐Doped Indium Oxide and Its Effects in Organic Optoelectronics

“…Optical transmission spectra reveal a maximum transmittance of 88.7% in ILTO sample A, and a slightly increased peak transmittance in sample B (91.7%) and C (91.3%). According to the sharp roll-off curves of transmittance in the ultraviolet region we have analyzed the energy bandgap property of samples by the relation between the incident photon energy and absorption coefficient: [34,35] …”