Optical and photoluminescence properties of nanostructured ZrO2:Tb thin films

Tb doped ZrO2 thin films were deposited on quartz substrates by sol-gel dip coating technique. X-ray diffraction patterns showed the formation of ZrO2:Tb thin films with a tetragonal structure. The morphological difference has been observed in the nanostructured ZrO2:Tb thin film with a terbium concentration of 5 mol% compared to other concentrations. An average transmittance of > 80% (in UV-Vis region) was observed for all samples. Optical band gap was found to vary as a function of doping concentration. ZrO2:Tb thin film with a terbium concentration of 5 mol% displayed a refractive index supremacy which can be directly employed in extending the range of tunability of the refractive index. Moreover, these films also demonstrated tuning of band gap values due to the incorporation of Tb into the solid networks of ZrO2 and modified microstructure. Photoluminescence (PL) properties showed several sharp lines due to terbium (Tb3 +) transitions. PL phenomena were observed, owing to the electronic structure of terbium (Tb3 +) ions as well as zirconia nanocrystallites in the films. Noticeable influences of terbium to terbium (Tb ↔ Tb) cross relaxation, which favors the green lines over the blue lines, are observed. An enhancement of luminescence intensity is found due to change in the crystalline environment and reduction in OH amount with temperature. The intense green PL emission in ZrO2:Tb thin films makes them suitable for generation of solid state light emitting diodes.