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

Abstract

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 631nm for the HfO2:Eu3+ films under excitation of 267nm. HfO2:Tb3+ films when excited at 277nm exhibit emission bands centered at 491, 543 (dominant emission), 551 and 586nm. In the case of co-doping with Eu3+ and Tb3+ ions white emission was observed under excitation with 320nm, as indicated by the CIE chromaticity diagram.