Effect of annealing on properties of sputtered and nitrogen-implanted ZnO:Ga thin films K.S. Shtereva, V. Tvarozek, I. Novotny, P. Sutta, M. Milosavljevic, A. Vincze, M. Vojs and S. Flickyngerova EPJ Photovolt., 3 (2012) 35003 Published online: 12 July 2012 DOI: 10.1051/epjpv/2012006