Structural, Optical and Luminescent Properties of ZnO:Eu 3+ Nanocrystals Prepared by Sol-Gel Method
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1174-V09-07
Structural, Optical and Luminescent Properties of ZnO:Eu3+ Nanocrystals Prepared by Sol-Gel Method S. Jáuregui-Rosas1,2, O. Perales Pérez3, W. Jia2, O. Vásquez2 and L. Angelats1 1 2 3
Materials Physics Laboratory-Department of Physics, Universidad Nacional de Trujillo, Av. Juan Pablo II S/N, Trujillo-Perú Department of Physics, University of Puerto Rico, Mayagüez, Puerto Rico, 00681-9016, USA Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044, USA
ABSTRACT Highly monodisperse ZnO:Eu3+ nanocrystals have been synthesized by modified sol-gel method from ethanolic solutions. The effect of Eu3+ ions (x=0.05-0.30) concentration on the structural, optical and luminescent properties has been evaluated. No other than the ZnO-wurtzite phase was observed at all dopant levels, which was confirmed by FT-IR and Raman spectroscopy techniques. A blue shift of the exciton peak and the increase on the corresponding band gap were observed at increasing Europium contents, which would indicate an interaction between Eu3+ ions and the development of the ZnO host structure. The luminescence properties were also dependent on Europium contents; a systematic blue shift and enhancement of the intensity of visible luminescence peak, attributed to an increment of surface defects, was observed by a rising Europium concentration. The red luminescence band, representing the 5D0→7F2 transition, was clearly observed in nanocrystals after annealing at 300oC for one hour. The presence of this band could be considered as an evidence of the effective energy transfer from ZnO to Eu3+ ions.
INTRODUCTION ZnO, a wide direct band gap (3.37eV) with a large exciton binding energy (60meV) material, is considered as one of the most promising semiconductor material for broad application spectra [1]. In particular, nanostructured ZnO has been proposed as host structure for rare-earth (RE) ions [2-6], being the Eu-doped ZnO system widely studied in recent years as nanorods [7], thin films [8] and nanoparticles [5,9]. These structures have been prepared using diverse routes including microemulsion [7], sol-gel [5], Pechini’s method [8], etc. Although several reports claimed that actual doping and energy transfer from ZnO host to Eu3+ ions take place [5-7], there is still controversy about the incorporation of large Eu ions into the ZnO lattice [8-12]. If possible, the synthesis of this type of doped semiconductor would open new applications due to its expected high light emission efficiency due to the Eu-Zn interactions between atomic states associated with the dopant and the host lattice material. Therefore, any effort to elucidate the formation of Eu-doped ZnO and understand the interactions between dopant and host lattice sounds justified. Accordingly, we investigated the synthesis of highly monodisperse ZnO nanocrystals containing Eu3+ ions by a modified sol-gel method and their structural, optical and luminescent characterization. The effect of annealing on the material functional propert
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