The chemical and optical features of nano-crystalline rare earth ions-doped (Er, Tb:) Si thin films, which were prepared by RF magnetron sputter techniques, were investigated as a function of the amount of Er and Tb doping on the Si films. The structural and chemical features are related with the photoluminescence (PL) phenomena of the films. The PL phenomena were observed, owing to the electronic structure of Er and Tb ions as well as Si nano-crystallites in the films. (C) 2004 Elsevier B.V. All rights reserved.