Effects of PEG1000 and Sol Concentration on the Structural and Optical Properties of Sol–Gel ZnO Porous Thin Films

Abstract

ZnO porous thin films were synthesized as antireflection coatings via a sol–gel dip-coating method with polyethylene glycol (PEG1000) utilized as a polymeric porogen on alumina transparent ceramics. The pore formation mechanism of the ZnO porous thin films was proposed through thermal and Fourier transformation infrared spectrometer (FTIR) analyses. The effect of sol concentrations on crystal structure, microstructure, and optical properties was also discussed. The experiment results indicated that all the ZnO thin films exhibited a hexagonal wurtzite structure with their preferred orientation along a (0 0 2) plane by X-ray diffraction (XRD) patterns. The grain size of the films increased from 30.5 to 37.4 nm with the sol concentration ranging from 0.2 to 1.0 M. Furthermore, scanning electron microscopy (SEM) images show that the pores on the surface were observed to first decrease as the sol concentration increased and then to disappear as the sol concentration continued to increase. The UV spectrum presents a maximum transmittance of 93.5% at a wavelength of 600 nm at a concentration of 0.6 M, which will be helpful in the practical applications of ZnO porous film on alumina transparent ceramic substrates. The pore formation mechanism of ZnO porous thin films can be ascribed to ring-like network structures between the PEG1000 and zinc oligomers under the phase separation effect.

Design of low cost waterborne polyvinyl alcohol coatings using plasticizer polyethylene glycol to minimize the residual solvent and coating defects

“…Chen et al 33 studied the synergistic effects of polyethylene glycol and organic montmorillonite (PEG/OMMT) on PLA films, and found that PEG/OMMT improved the elongation at break, mechanical strength, and thermal stability of the films. Xu et al 34 prepared zinc oxide porous films with dip‐coating method and studied the effect of PEG‐1000 on it. It was observed that PEG‐1000 acted as polymeric porogen and promoted the formation of uniform pores in the film.…”

Novel Antireflection Coatings Obtained by Low-Temperature Annealing in the Presence of Tetrabutylammonium Bromide and Gold Nanoparticles

“…For the matrix refractive index n ~ 1.46 (in the case of SiO 2 ), the porosity of 0.45–0.50 ensures n ~ 1.23 of a single-layer anti-reflective coating [ 19 ]. For this purpose, various pore-generating agents, such as surfactants, are used [ 20 , 21 ]. Determining the optimum gel temperature and annealing time is one of the challenges in achieving antireflective parameters on silicate glass.…”