Effect of structure and composition on optical properties of Er-Sc silicates prepared from multi-nanolayer films

Polycrystalline Er-Sc silicates (Er(x)Sc(2-x)SiO₅ and Er(x)Sc(2-x)Si₂O₇) were fabricated using multilayer nanostructured films of Er₂O₃/SiO₂/Sc₂O₃ deposited on SiO₂/Si substrates by RF- sputtering and thermal annealing at high temperature. RBS, TEM, GIXD, and PL results show the presence of Er(x)Sc(2-x)SiO₅ with an emission peak at 1528 nm for annealing from 900 to 1100 °C, and Er(x)Sc(2-x)Si₂O₇ with an emission peak at 1537 nm for higher annealing temperature. The PL intensity of the Er(x)Sc(2-x)Si₂O₇ phase is five times stronger than that of the Er(x)Sc(2-x)SiO₅ phase at 1250 °C. From PLE and PL spectra of Er(x)Sc(2-x)Si₂O₇ thin film, we schematically illustrate the Er³⁺ Stark energy levels of ⁴I(13/2) to ⁴I(15/2) manifolds due to the crystal field strength effect of Sc³⁺. Temperature-dependent PL of the Er(x)Sc(2-x)Si₂O₇ phase exhibits a variation of the full-width at half-maximum (FWHM) from 1.1 to 2.3 nm. The narrow FWHM is due to the small ionic radii of Sc³⁺, which enhance the crystal field strength affecting the optical properties of Er³⁺ ions located at the well-defined lattice sites of Sc silicate. A large excitation cross-section (σ(ex)) is equal to 3.0x10⁻²⁰ cm² at λ(ex) = 1527.6 nm.