OPTICAL CHARACTERIZATION OF IN-SITU GENERATED CU2O EXCITONS IN SOLUTION DERIVED NANO-ZIRCONIA FILM MATRIX

Cu2O excitons were generated in-situ in a nano-zirconia film matrix on silica glass substrate from the precursor solution containing Cu(II) nitrate trihydrate and zirconium oxychloride octahydrate. The films we re annealed in the temperature range 200-1200 degrees C and characteri zed by transmission electron microscopy (TEM), UV-VIS-NIR and fluoresc ence spectroscopy. In the UV-VIS spectra of the films most of the UV a nd visible bands shifted towards longer wavelengths with increasing an nealing temperature and the corresponding Cu2O microcrystallite size w as evaluated from the shifting of the UV bands (271-371 nm). Wannier h ydrogen-like excitonic transitions, e.g., blue, green, yellow series o f Cu2O excitons were observed in the visible region. Excitation depend ent fluorescence bands were observed in the visible region and the 400 nm excitation depicted two distinct fluorescence bands in the green ( similar to 525 nm) and red (similar to 630 nm) regions. The intensity ratios of green and red fluorescences and vice versa were found to be dependent on the microcrystallite size. Tentative band assignments hav e been proposed from the excitonic absorption and fluorescence bands.