Séminaire LMGP - 20/01/2016 - Sergio BATTIATO

In the past few years, fluoride materials have attracted a great and increasing interest due to their multifunctional properties, such as ferroelectricity, induced ferro/antiferromagnetism, thermal stability, high transparency and low phonon energy. Among the few known ferroelectric fluoride crystals, the barium fluoride BaMF₄ (M=Mg, Mn, Co, Ni, Zn) phases have recently caught substantial attention in view of their interesting and multifunctional properties. The BaMF₄ multiferroics have been proposed as systems where is possible to incorporate both magnetism and ferroelectricity in the same phase. In addition, fluoride compounds have compelling advantages for many optical applications due to their unique combination of low phonon energy, high UV absorption edge energy, and relatively weak crystal field.

Compared with oxides, fluorides are considered to be efficient hosts for down-conversion (DC) and upconversion (UC) luminescence of rare earth (RE) ions due to their low phonon energies and optical transparency over a wide wavelength range. The choice of host materials is of great importance in designing lanthanide-based luminescent UC materials for efficient practical applications. Among the fluorides reported, rare earth (RE) doped NaYF₄ and NaGdF₄ are considered as the most efficient DC and UC host lattices, and have recently raised increasing attention. Trivalent RE-doped MF₂ ( with M=Sr, Ca, Ba) compounds are also considered a suitable material characterized by low energy phonons (usually less than 300 cm^-1) and large transfer coefficients between the RE ions. In this tipology of halide hosts, multiphonon relaxation is thought to be strongly suppressed and therefore efficient UC luminescence can be obtained. In this talk, I will present the Metal Organic Chemical Vapor Deposition (MOCVD) fabrication of the fluoride phases of interest in thin film form and a systematic study of precursors suitable for the MOCVD growth of the fluoride films which possess physical properties of great technological interest.