X-RAY EXCITED LUMINESCENCE AND LOCAL STRUCTURES IN TB-DOPED Y2O3 NANOCRYSTALS

Pronounced structure in x-ray excited luminescence (XEL) has been obse rved in dilute Tb-doped Y2O3 (Y2O3:Tb) nanocrystals. This effect affor ds a means to assess different energy transfer mechanisms in the nanoc rystals and also an opportunity for novel device applications. Sharp j umps and oscillations are found in the XEL output with the incident x- ray energy around the absorption edges of Y and Tb. When compared with a bulk Y2O3:Tb sample, these effects are attributed to some unique el ectronic and optical properties of doped nanocrystals related to quant um confinement of charge carriers, and the main features can be explai ned by a proposed model of multichannel energy transfer. Extended x-ra y absorption fine structure techniques have also been employed to stud y the effect of size variation and chemical doping on the local struct ures in Y2O3 and Y2O3:Tb nanocrystals. The local environment surroundi ng Y and Tb in the nanocrystals is compared with that in the respectiv e bulk material. The results indicate that Tb impurity atoms substitut e for Y sites in bulk Y2O3, while doping in the nanocrystals is compli cated by the large fraction of surface atoms and local disorder. (C) 1 998 American Institute of Physics.