Blue and green emission from Ho3+ doped zinc titanate phosphor thin films by sol-gel

Zinc titanate ZnTiO3 phosphor thin films doped with 1, 2, and 3 mol% of Ho3+ ions were fabricated using sol-gel method a combined with dip-coating technique on silica glass substrate and subsequent thermal annealing in the range of 600-900 degrees C. Effects of annealing temperature and Ho3+ ions concentration on the structure and optical properties of these phosphor thin films were investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible transmittance spectroscopy, excitation, and emission spectroscopy. Results revealed that ZnTiO3 nanocrystals were formed upon 600 degrees C annealing temperature. At 900 degrees C polycrystalline films including ZnO and TiO2 anatase phase were observed. The average diameter of nanocrystals showed temperature dependence and was varied in the range-over 15-48 nm which was revealed by SEM images with cracks free. The EDS showed homogenous distribution of Ho3+ ions in the thin film specimens. It was found that Ho3+ ions incorporated into the nanocrystals. As a result, the room temperature luminescence color emission of the synthesized phosphor thin film specimens can be tuned from blue to green by switching the excitation wavelength from 360 nm to 430 nm. The achieved result makes these phosphor thin films promising for several applications such as optoelectronics and light-emitting.