Effect of Glymo on the Morphological and Optical Properties of Eu³⁺-Doped Lu₂SiO₅ Films

Eu³⁺-(5% mol)-doped Lu₂SiO₅ optical quality films were prepared using the sol–gel method and dip-coating technique from lutetium and europium salts as the lanthanide precursors and tetraethyl orthosilicate (TEOS) as the silicon source. To increase the thickness of the films, 3-Glycidyloxypropyl trimethoxysilane (Glymo) was added as the rheological agent during sol formation. Structural, morphological, and luminescent properties were investigated for Lu₂SiO₅, Eu³⁺:Lu₂SiO₅, and Eu³⁺:Lu₂SiO₅/Glymo in order to obtain high quality in luminescent films. X-ray diffraction (XRD) results show that the incorporation of the Eu³⁺ ions do not affect the A-Type and B-Type monoclinic crystalline phase typical of Lu₂SiO₅, even after five dipping cycles on quartz substrates and a final annealing process at 1100 °C. The morphology and topography of the films were studied by SEM and AFM. These techniques revealed films without surfactant that were uniform with low rugosity while the film with surfactant presented porous hills and valleys with uneven high values of roughness. The photoluminescence spectrum of Eu³⁺:Lu₂SiO₅ films showed 2 broad emission peaks centered at 589 nm and 612 nm. The presence of Glymo in the system promoted the formation of residual Lu₂Si₂O₇ compounds with the highest lifetime values compared with films without surfactant. The results of the films are promising for luminescent applications.