Near-infrared light emission of Er3+-doped zirconium oxide thin films: an optical, structural and XPS study - Clabel H., J. L.; Rivera, V. A. G.; Siu Li, Máximo; Nunes, Luiz Antônio de Oliveira; Leite, E. R.; Schreiner, W. H.; Marega Junior, Euclydes (Journal of Alloys and Compounds, 2015)