Er 3 + excited state absorption and the low fraction of nanocluster-excitable Er3+ in SiOx

Abstract
Despite the observation by a number of groups of a strong luminescence sensitization effect of erbiumions by excitation exchange from siliconnanoclusters, there is considerable experimental evidence that the fraction of Er ions excited by Si-nc is actually very low for much of the material reported. In this work, we examine the evidence and point out that Er excited state absorption is the likely cause.