@article{articledf3a469f,
title   = {Optical properties of Er and Er + Yb doped hydrogenated amorphous silicon films},
author = {Oliveira, V. I. and Freire Junior, Fernando Lázaro and Zanatta, Antonio Ricardo},
year = {2006},
doi = {10.1088/0953-8984/18/32/018},
journal   = {Journal of Physics: Condensed Matter}
}