Luminescent properties of innovative Eu-doped lanthanum oxyfluoride sol-gel thin films

Highly luminescent Eu3+-doped LaOF thin films have been prepared by a sol-gel procedure using La(hfa)3 diglyme (Hhfa ) 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme ) bis(2-metoxyethyl)ether) as a singlesource precursor for lanthanum and fluorine. Europium doping (Eu/La ) 3 and 10 atom %) has been achieved by adding the proper amount of europium acetate hydrate (Eu(CH3CO2)3 · xH2O, x =1- 4) to the precursor solution. After single-layer deposition, the obtained coatings were heat treated in air up to 700 °C. All the samples, under UV irradiation, presented a bright red luminescence clearly visible to the naked eye notwithstanding the low europium content and the limited film thickness (ca.50 nm). The microstructure, composition, and morphology of the samples and their interplay with the synthesis conditions were investigated by glancing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and field emission scanning electron microscopy (FE-SEM). The luminescence properties of Eu3+:LaOF in the energy and time domains are reported and discussed as a function of europium content and synthesis conditions. The observed variations in the light-emitting behavior of Eu3+ ions have been correlated to the structural and compositional characteristics of the host oxyfluoride matrices.