Mechanisms of Zinc Oxide Nanocrystalline Thin Film Formation by Thermal Degradation of Metal-Loaded Hydrogels

Thermal degradation of metal-loaded hydrogel films is a powerful tool to synthesize high-quality metal oxide thin films with nanometric grain size, but the formation mechanism is still poorly known. We exploited fluorescence X-ray absorption fine structure as a short-range probe to investigate the f...

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Bibliographic Details
Published in:Journal of physical chemistry. C 2013-11, Vol.117 (47), p.25108-25117
Main Authors: Tredici, Ilenia G, Resmini, Alessandro, Pin, Sonia, Ghigna, Paolo, Rovetta, Tommaso, Patrini, Maddalena, Rotiroti, Nicola, Dapiaggi, Monica, Anselmi-Tamburini, Umberto
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Equations of state, phase equilibria, and phase transitions
Exact sciences and technology
General studies of phase transitions
Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties
Materials science
Nanocrystalline materials
Nanoscale materials and structures: fabrication and characterization
Nucleation
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
Physics
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
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Summary:Thermal degradation of metal-loaded hydrogel films is a powerful tool to synthesize high-quality metal oxide thin films with nanometric grain size, but the formation mechanism is still poorly known. We exploited fluorescence X-ray absorption fine structure as a short-range probe to investigate the first stages of nucleation and the following development of ZnO nanoparticles in Zn-loaded hydrogels, annealed for 20 min at temperatures between 150 and 500 °C. The experimental results evidenced that the first nuclei of ZnO begin to form at 300 °C, whereas at 350 °C the ZnO nanoparticles are already well crystallized. By coupling the results with those obtained by thermal analysis, profilometry, HR-TEM, diffraction and μ-FTIR, a formation mechanism was suggested. The optical and electrical properties of the samples confirm that the polymer forms an insulating shell around the nanoparticles up to 450 °C: the intimate hybridization promotes stress relaxation during the annealing, yielding crack-free metal oxide films. Prolongation of the annealing time allowed the removal of the organic shell at 350 °C, yielding fully conductive, transparent ZnO films with particle size reduced to 7 nm.
ISSN:1932-7447
1932-7455
DOI:10.1021/jp407993q