White light generation from HfO₂ films co-doped with Eu³⁺+ Tb³⁺ ions synthesized by pulsed laser ablation technique

In this work we investigate the luminescent properties of HfO₂ films doped with Eu³⁺, Tb³⁺ and Eu³⁺+ Tb³⁺ ions excited through photoluminescence and cathodoluminescence. These films were synthesized by the pulsed laser ablation technique and structurally studied by X-ray diffraction and Raman spectroscopy; the surface morphology was observed by scanning electron and atomic force microscopies. The optical transmittance was measured as well. The crystalline phase observed was the monoclinic of the HfO₂. The surface morphology of the films exhibited a low roughness, as measured by atomic force microscopy. These films show a high transparency in the visible region. The emission spectra show bands centered at 598, 614 (strongest emission), and 631 nm for the HfO₂:Eu³⁺ films under excitation of 267 nm. HfO₂:Tb³⁺ films when excited at 277 nm exhibit emission bands centered at 491, 543 (dominant emission), 551 and 586 nm. In the case of co-doping with Eu³⁺ and Tb³⁺ ions white emission was observed under excitation with 320 nm, as indicated by the CIE chromaticity diagram.