Synthesis and fabrication of Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺ thin films for electroluminescent applications: Optical and structural characteristics

Terbium, europium and yttrium β diketonates have been synthesized from acetylacetone and inorganic metal salts and used as precursors for the deposition of Tb³⁺ or Eu³⁺ doped Y₂O₃ polycrystalline films by the ultrasonic spray pyrolysis technique. The films were deposited on c-Si substrates at temperatures in the 400-550 °C range. The optical and structural characterization of these films as a function of substrate temperature and Tb³⁺ and Eu³⁺ concentration was carried out by means of photoluminescence (PL), cathodoluminescence (CL), infrared (IR), ellipsometry, and UV-visible spectroscopy and atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and X ray diffraction (XRD) measurements respectively. The PL intensity from these films was found to depend on deposition temperature. Films deposited above 450 °C exhibited the characteristic PL peaks associated with either Tb³⁺ or Eu³⁺ intra electronic energy levels transitions. The most intense PL emission was found for dopant concentration of 10 at% for Tb³⁺ and at 8 at% for Eu³⁺ ions into precursor solution. In both cases concentration quenching of the PL emission was observed for concentrations above these values. The films had a refractive index (1.81), low average surface roughness (∼62 Å) and a UV-Vis. transmission of the order of 90 %T.