Instituto de Óptica “Daza de Valdés”

Optical properties of nanostructures based on divalent europium-doped barium fluoride layers fabricated by pulsed laser deposition (PLD)

7 Feb, 2022 | LPG-en

Advancing towards white light emission based on europium nanostructures.

Submicron thick thin films are used in a wide variety of optical applications. Current potential applications include the emission of white light and photovoltaic energy. Its capabilities depend fundamentally on its composition and structure since they determine its optical response, so that the use of new synthesis techniques that allow its control at the nanoscale level provide us with new possibilities.
In this study, thin-film nanostructures formed by nanocrystalline layers of Barium fluoride (BaF2) doped with Eu2+ separated by layers of aluminum oxide (Al2O3) by sequential pulsed laser deposition in vacuum. This technique makes it possible to create layers with nanometric thicknesses, as well as to control the distribution of the Eu2+ dopant within the layer.
After fabrication, the nanostructures underwent thermal annealing in a nitrogen atmosphere to activate the luminescence of Eu2+, preventing its oxidation. The results show how the nanostructures produced emit light with chromatic characteristics close to those of pure white light.

The objective of this study is to understand the optical properties of these nanostructures to determine what should be the optimal configuration for the design of a white light-emitting LED based on these materials.

Últimas noticias


Solid-state light-emitting diode (LED) lighting has many advantageous features including low power consumption, high brightness, and long lifespan.

Current white light emitting diode technology is based either on a blue LED combined with a phosphor (YAG: Ce3+) coated with epoxy resin, or on the combination of two excitation sources UV or blue with different phosphors doped with rare earths that emit blue, green and red light. Both solutions are complex and have limited performance, so a white light LED based on a single material would result in a simpler manufacturing process.


Divalent europium (Eu2+) exhibits light emission in a broad band of the visible spectrum. This emission is due to the electronic transition 4f65d1 to 4f7 that occurs in the external orbitals of the atom. For this reason, this transition is very sensitive to the crystalline field and, therefore, to the nanostructure and configuration of the material, unlike what occurs in the case of Eu3+.

A lower energy leads to a TiO2 phase with a lower TiN contribution, while a higher fluence produces a greater amount of TiN.
This is a collaborative effort between the Optical Institute’s Laser Processing Group, the University of Tennessee Space Institute’s Department of Mechanical, Aerospace, and Biomedical Engineering, the University of Tennessee Space Institute’s Center for Laser Applications, the Department of Engineering and Materials Science at Northwestern University in Evanston and the Division of Materials Science at Argonne National Laboratory.

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