Speaker
Mr
ABDUB ALI
(UNIVERSITY OF THE FREE STATE)
Description
1. Introduction
Eu3+- doping has been of interest to improve the luminescent characteristics of thin-film phosphors. Europium-doped Y2O2S exhibits strong UV and cathode ray-excited luminescence, so it is widely used as red phosphors for low-pressure fluorescent lamps, cathode-ray tubes and plasma display panels [1]. Also, the hexagonal Y2O2S is a good host material for rare earth ions. In recent years, the Y2O2S: Eu has received much attention for its tremendous potential applications in optical display and lighting materials and basic science research on special luminescent spectra. Nanoscale and thin film Y2O2S: Eu has remarkably different luminescent properties from those of bulk samples: such as emission line broadens, lifetime changes and its spectra shift [2]. In this study Y2O2S: Eu thin films have been deposited with the pulsed laser deposition technique in an O2 environment. The oxygen pressure was changed from 0 to 140 mtorr.
2. Results
The X-ray diffraction patterns (Fig.1) show mixed phases of cubic and hexagonal crystal structures. As the oxygen partial pressure increased, the crystallinity of the films improved. Further increase of the O2 pressure to 140 mtorr reduced the crystallinity of the film. Similarly, both scanning electron microscopy and atomic force microscopy confirmed that an increase in O2 pressure affected the morphology of the films. The average band gap of the films calculated from diffuse reflectance spectra using the Kubelka-Munk function was about 4.75 eV. The photoluminescence measurements (Fig.2) indicate red emission of Eu3+ doped Y2O2S thin films with the most intense peak appearing at 619 nm, which is assigned to the 5D0-7F2 transition of Eu3+. This most intense peak is totally quenched at higher O2 pressures. This phosphor may be good promising material for applications in the flat panel displays.
Please provide the name and email address of your supervisor.
Prof. Francis B. Dejene
dejenebf@qwa.ufs.ac.za
Are you currently a postgraduate student? (Yes/No)
YES
At what level of studies are you currently? (Hons/MSc/PhD)
PhD
Primary author
Mr
ABDUB ALI
(UNIVERSITY OF THE FREE STATE)
Co-authors
Prof.
FRANCIS DEJENE
(UNIVERSITY OF THE FREE STATE)
Prof.
HENDRIK SWART
(UNIVERSITY OF THE FREE STATE)
