Eu3+ doped yttrium oxysulfide quantum structures-structural, optical and electronic properties

Small particles of trivalent europium doped yttrium oxysulfide nanocrystals (phi similar to 7 nm) were synthesized using sol-gel polymer thermolysis. The nanocrystals show significant change in the excitation bands corresponding to fundamental absorption and charge transfer absorption bands. The optical spectra essentially comprise of two parts: fundamental absorption (similar to 260 nm) and Eu3+-X2- ligand (O2-/S2-) charge transfer (similar to 290 nm) bands. They show significant blue shifts (0.24-0.30 eV), respectively, with respect to the bulk counterpart. These may be explained by considering possible size dependent changes associated with quantum confinement effect in this large bandgap semiconductor system. FT-IR spectra revealed the difference in chemisorbed species between bulk and nanocrystalline samples. The results of the solid-state photo-induced electrical impedance spectroscopy studies are reported.