Blue-green-red luminescence from CeCl3-and MnCl2-doped hafnium oxide layers prepared by ultrasonic spray pyrolysis

Hafnium oxide films doped with CeCl(3) and/or MnCl(2), and deposited at 300 degrees C by an ultrasonic spray pyrolysis process, were characterized using x-ray diffraction (XRD), energy-dispersive spectroscopy and photoluminescence. The XRD results revealed that the films are predominantly amorphous. The weak green-red emission of Mn(2+) is enhanced through an efficient energy transfer from Ce(3+) to Mn(2+) ions. Spectroscopic data revealed that the energy transfer is nonradiative in nature and it could occur in Ce(3+) and Mn(2+) clusters through a short-range interaction mechanism. The efficiency of this transfer increases with the Mn(2+) ion concentration, so that an efficiency of about 78% is attained for a 5 at.% of MnCl(2) concentration, which makes these films interesting phosphors for the design of luminescent layers with blue, green and red emissions.