Li+ Co-Doping Effect on the Photoluminescence Time Decay Behavior of Y2O3: Er3+ Films

Wednesday, 8 October 2014
Expo Center, 1st Floor, Center and Right Foyers (Moon Palace Resort)
A. Meza.Rocha (Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física.), E. Huerta (Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV IPN, Av. IPN 2508, México DF, 07360 México), E. Zaleta-Alejandre (Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física), and C. Falcony (Centro de Investigación y Estudios Avanzados, Instituto Politécnico Nacional, Departamento de Física)
The incorporation of rare earth ions in metal oxides has received considerable attention for great variety of applications such as, biomedical, optical amplifier, active waveguide, solar cell, etc. In particular, Er3+ ion shows interesting characteristic emissions in the 520-580, 640-700, 1520-1580 nm ranges, which are suitable for most of the applications mentioned above. The use of thin film phosphors offers some advantages over bulk powders such as a better thermal stability, better adhesion, and good uniformity coverage of substrate surfaces. However, the main drawback of phosphor films has been their low brightness in comparison with bulk powders. Recently, it has been reported that the incorporation of Li+, Na+ and K+ alkali ions enhances considerably the luminescent efficiency of rare earths. In this work, the effect of Li+ co-doping on photoluminescent time decay characteristics of Y2O3: Er3+ is reported for films deposited by ultrasonic spray pyrolysis at 500°C. The Er3+ content was fixed at 1.5 at% while the Li+ content in the spraying solution was varied from 1 to 4 at% in relation to Y3+. It is observed that the addition of Li+ content up to 2 at%, besides resulting in an increase of the luminescence emission intensity, modifies the luminescence time decay behavior as well. In general, the decay profiles under 207 and 414 nm excitation are not fitted to a simple exponential. They seem to be composed by an initial slow decay followed by a faster decay. This behavior is associated with a charge transfer process.  A simple model in which charge transfer from localized centers to the Er3+ ions is used to describe the evolution with time of the luminescence emission. The introduction of Li+ ions in the Y2O3: Er3+ seems to have an impact on both the effectiveness of the charge transfer process and on the total number of Er3+ ions contributing to the luminescence emission.