Surface electronic structure and mechanical characteristics of copper-cobalt oxide thin film cCoatings: Soft X-ray synchrotron radiation spectroscopic analyses and modeling

Document Type

Journal Article


American Chemical Society


Faculty of Health, Engineering and Science


School of Engineering




This article was originally published as: Amri, A., Jiang, Z., Bahri, P., Yin, C., Zhao, X. , Xie, Z. , Duan, X., & Widjaja, H., Rahman, M., Pryor, T. (2013). Surface Electronic Structure and Mechanical Characteristics of Copper-Cobalt Oxide Thin Film Coatings: Soft X-ray Synchrotron Radiation Spectroscopic Analyses and Modeling. The Journal of Physical Chemistry C, 117(32), 16457-16467. This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp404841m


Novel copper-cobalt oxide thin films with different copper/cobalt molar ratios, namely, [Cu]/[Co] = 0.5, 1, and 2, have been successfully coated on aluminum substrates via a simple and cost-effective sol-gel dip-coating method. Coatings were characterized using high resolution synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy, in combination with nanomechanical testing and field emission scanning electron microscopy (FESEM). The surfaces of both [Cu]/[Co] = 0.5 and 1 samples consisted primarily of fine granular nanoparticles, whereas the [Cu]/[Co] = 2 has a smoother surface. The analyses reveal that the increase of copper concentration in the synthesis process tends to promote the formation of octahedral Cu2+ which minimizes the development of octahedral Cu+, and these octahedral Cu2+ ions substitute the Co2+ site in cobalt structure host. The local coordinations of Co, Cu and O are not substantially influenced by the change in the copper to cobalt concentration ratios except for the [Cu]/[Co] = 2 coating where the local coordination appears to slightly change due to the loss of octahedral Cu+. The present film coatings are expected to exhibit good wear resistance especially for the [Cu]/[Co] = 1.0 sample due to its high hardness/elastic modulus (H/E) ratio. Finite element modeling (FEM) indicated that, under spherical loading conditions, the high stress and the plastic deformation were predominantly concentrated within the coating layer, without spreading into the substrate.