Combinatorial sputtering of photoluminescent europium titanium oxide thin films

Photoluminescent thin films were fabricated using a combinatorial physical vapour deposition (PVD) sputtering process, enabling rapid variation of europium oxide (Eu₂O₃) in titanium dioxide (TiO₂) with concentrations varying from x = 0-1 in x = Eu/(Eu + Ti). Combinatorial sputtering enables synthesising samples with diverse compositions faster than traditional sol-gel, powder mixing, solvo/hydrothermal, and melt-quench processes. Post-heat treatment at 600 °C produced changes to the phase, structure and optical properties of the thin films. Scanning electron microscopy (SEM) revealed vertically oriented columnar microstructures in samples with concentrations lower than x = 0.5, exhibiting a narrower average columnar width of about 50 nm after annealing at 600 °C. X-ray diffraction (XRD) analysis indicated that TiO₂ was in the anatase phase while Eu₂O₃ crystallises in a monoclinic structure. The nanocrystalline grain size exhibits noticeable changes after annealing. Fluorescence spectroscopy was used to study the photoluminescence of thin films. The excitation peak at 394 nm (⁷F₀ → ⁵L₆) measures spectral emissions, with the strongest emission at 613 nm (⁵D₀ → ⁷F₂).