Cold white light generation from hafnium oxide films activated with Ce~(3+), Tb~(3+), and Mn~(2+) ions

摘要

Hafnium oxide films doubly doped with CeCl_3 and TbCl_3 and triply doped with CeCl_3, TbCl_3, and MnCl_2 were deposited at 300℃ with the ultrasonic spray pyrolysis technique. The green and yellow emissions of Tb~(3+) ions and the yellow-red emission of Mn~(2+) ions can be generated upon ultraviolet (UV) excitation via a nonradiative energy transfer from Ce~(3+) to Tb~(3+) and Ce~(3+) to Mn~(2+). In the doubly doped film Ce~(3+)→ Tb~(3+) 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 HfO_2 films activated with Ce~(3+), Tb~(3+), and Mn~(2+) the efficiency of energy transfer from Ce~(3+) to Tb~(3+) and Mn~(2+) ions is enhanced by increasing the Mn~(2+) 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).