Control of the formation and luminescent properties of polymorphic erbium silicates on silicon

Abstract

We report on the control of the formation and the luminescent properties of polymorphic forms of erbium (Er) silicates by the modification of annealing temperatures, annealing atmospheres and chemical compositions. Four Er silicate polymorphs, X1-Er2SiO5, y-Er­2Si2O7, α-Er2Si2O7 and β-Er2Si2O7, are fabricated in Er-doped SiO2 films. Higher annealing temperatures turn the Er silicates into more stable polymorphs, but the annealing in O2 and the deviation of chemical compositions from the stoichiometry of Er silicates will restrain this process. The luminescent properties of these polymorphs are quite different due to their strong correlation with the crystallographic structures. Photoluminescence spectra with the main peaks at 1530 nm, 1536 nm, 1529 nm, and 1539 nm are obtained for X1-Er2SiO5, y-Er­2Si2O7, α-Er2Si2O7 and β-Er2Si2O7, respectively, and the highest photoluminescence efficiency is associated to Er ions in y-Er2Si2O7.