Optical evaluation of doping concentration in SiO2 doping source layer for silicon quantum dot materials T. Zhang, I. Perez-Wurlf, B. Berghoff, S. Suckow and G. Conibeer EPJ Photovolt., 2 (2011) 25001 Published online: 29 September 2011 DOI: 10.1051/epjpv/2011024