Sputtered zinc oxide coatings: structural study and application to the photoprotection of the polycarbonate

• Published in: Surface & coatings technology Vol. 180; pp. 642 - 645
• Main Authors: Moustaghfir, A., Tomasella, E., Rivaton, A., Mailhot, B., Jacquet, M., Gardette, J.L., Cellier, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2004; Elsevier
• Subjects: Analytical chemistry; Chemical Sciences; Material chemistry; or physical chemistry; Photoprotective coating; Polycarbonate; Polymers; Structure; Theoretical and; ZnO deposits; Photoprotective coating; Structure; Polycarbonate; ZnO deposits
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2003.10.109

Zinc oxide (ZnO) was deposited by sputtering on silicon substrates. The structure and the composition of these deposits were studied by X-ray diffraction and Rutherford backscattering spectrometry, respectively. It was found that the thin films are polycrystalline with an hexagonal würtzite structure and have a crystallographic c-axis orientation perpendicular to the substrate surface. When the thickness of the coatings increases from 50 to 600 nm, the grain size and the density increase whereas the O/Zn atomic ratio decreases. Then ZnO coatings were deposited on bisphenol-A polycarbonate (PC) films in order to protect this polymer against the solar ultraviolet (UV) radiations. Samples were irradiated in artificial accelerated conditions with a polychromatic light (λ>300 nm). The rate of photodegradation was evaluated by infrared and UV–visible spectroscopies. ZnO coatings decrease the rate of oxidation and the rate of photo-yellowing of PC. The efficiency of the ceramic coating depends on its thickness and its structural properties. As a conclusion, ZnO coatings can improve the long-term behaviour of PC for outdoor applications.