Eu 3+ as optical probe of the structure in amorphous and nanocrystalline ZnO sol-gel films E. Terán-Hinojosa 1 , J.A. García-Macedo 1,* , G. Valverde-Aguilar 2 1 Departamento de Estado Sólido. Instituto de Física, Universidad Nacional Autónoma de México. México D.F. C.P. 04510. 2 CICATA Unidad Legaria, Instituto Politécnico Nacional. Legaria 694, Col Irrigación, Miguel Hidalgo, 11500 Ciudad de México, Distrito Federal, Mexico. * Corresponding author: Dr. Guadalupe Valverde-Aguilar Address: Legaria 694, Col Irrigación, Miguel Hidalgo, C. P. 11500 Ciudad de México, Distrito Federal, Mexico. Tel. (52 55) 57296000 ext. 67763, Fax (52 55) 53293255 Email: mvalverde@ipn.mx , valverdeag@gmail.com ABSTRACT. Amorphous and nanocrystalline Eu 3+ -doped ZnO thin films were synthesized by the sol –gel process. The films were spin-coated on glass substrates. The samples were annealed at 500°C for 1 hour to produce a nanocrystalline ZnO/Eu 3+ films. The samples were characterized using UV-Vis absorption and infrared spectroscopy. A crystalline phase, wurtzite, was detected by X-ray diffraction. A spectroscopic study of the Eu 3+ impurity in function of the heat treatment provided to the ZnO matrix was done. Results of emission and excitation studies at room temperature of Eu 3+ inserted in the ZnO matrix are presented. For amorphous and nanocrystalline samples, the relative ratio of the 7 F2/ 7 F1 transitions was calculated. The evolution of this ratio was interpreted in terms of the Eu 3+ symmetry site change when the nanocrystalline ZnO films. This fact was confirmed measuring the Eu 3+ lifetimes. Keywords: rare earth, zinc oxide, sol-gel, optical absorption, luminescence, lifetimes 1. INTRODUCTION Zinc oxide (ZnO) has a wide and direct band gap of 3.36 eV at room temperature and a higher exciton binding energy (60 meV), which assures more efficient exciton emission at higher temperatures, compared with other wide band gap materials, such as GaN (28 meV) and ZnSe (19 meV) 1–3 . In addition, ZnO can be deposited at lower temperature than GaN. Owing to these properties, ZnO has received much attention as a candidate material for opto- electronic devices such as UV laser diodes and UV-blue light-emitting diodes. ZnO has been studied in different growth forms such as nanoneedles, nanowires, nanorods, flowers, tetrapods, etc 4–8 for its luminescence properties. In particular, ZnO powders and thin films are very important materials in ceramic technology and thin films technology due to numerous properties 9 . ZnO powder with suitable dopants is used as a photoconductor in electrophotography, a varistor in ceramic technology, a sensor element in sensing combustible gases and additive in various ferrites. As a thin film exhibits piezoelectric properties which are used in various pressure transducers and acousto-optic devices, surface and bulk acoustic wave devices, solar cells, piezoelectric transducers 10 . Nanophotonic Materials IX, edited by Stefano Cabrini, Taleb Mokari, Proc. of SPIE Vol. 8456, 845603 · © 2012 SPIE · CCC code: 0277-786/12/$18 · doi: 10.1117/12.929114 Proc. of SPIE Vol. 8456 845603-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 11/13/2012 Terms of Use: http://spiedl.org/terms