Preparation and characterization of ultrafine neodymium oxide/TiO₂/ORMOSIL sol-gel composite thin film

Neodymium oxide nanoparticles/TiO₂/ORMOSIL composite sol-gel thin films have been prepared by combining an inverse microemulsion technique and the sol-gel technique at low temperature. Transmission electron microscopy and scanning electron microscopy have been used to characterize the size and structural properties of the neodymium oxide nanoparticles and composite thin films. Photoluminescence and up-conversion emission properties of these composite thin films deposited on silicon substrates have been studied. A relatively strong room-temperature photoluminescence emission at 1064 nm corresponding to the ⁴F_3/2→⁴I_11/2 transitions from these composite thin films has been observed as a function of the heat treatment temperature. An intense up-conversion emission in violet (402nm corresponding to ⁴D_3/2→⁴I_13/2 transitions) color from the composite thin films baked at different temperatures upon excitation with a yellow light (587nm) has been observed. In addition to this violet emission, an UV emission at 372 nm and a weak blue emission at 468 nm have been obtained. The mechanism of the up-conversion emission has been explained by means of an energy level diagram. The lifetimes of the violet emissions have been measured.