a1 Instituto de Física y Matemáticas, Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca 69000, México
a2 Departamento de Física, Universidad de Sonora (UNISON), Hermosillo, Sonora 83000, México
a3 DiSTeMeV, Università di Verona, and INSTM, UdR Verona, I-37029 San Floriano, Verona, Italy
a4 Centro de Investigación y de Estudio Avanzados del IPN, Departamento de Física, 07000 México, D.F., México
a5 Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, 09340 México, D.F., México
Hafnium oxide films doubly doped with CeCl3 and TbCl3 and triply doped with CeCl3, TbCl3, and MnCl2 were deposited at 300 °C with the ultrasonic spray pyrolysis technique. The green and yellow emissions of Tb3+ ions and the yellow-red emission of Mn2+ ions can be generated upon ultraviolet (UV) excitation via a nonradiative energy transfer from Ce3+ to Tb3+ and Ce3+ to Mn2+. In the doubly doped film Ce3+ → Tb3+ energy transfer via an electric dipole–quadrupole interaction appears to be the most probable transfer mechanism; the efficiency of this transfer is about 81% upon excitation at 270 nm. In the HfO2 films activated with Ce3+, Tb3+, and Mn2+ the efficiency of energy transfer from Ce3+ to Tb3+ and Mn2+ ions is enhanced by increasing the Mn2+ concentration, up to about 76% for the film with the highest manganese content (1.6 at.%). In addition, it is demonstrated that these triply doped films can generate cold white light emission upon excitation at 270 nm (peak emission wave length of an AlGaN/GaN-based LEDs).
(Received September 15 2009)
(Accepted December 09 2009)