TOF-SIMS and laser-SNMS investigations of dopant distribution in nanophosphors

Abstract

Characterization of industrially important nanophosphors such asZnS:Mn2+,SrAl2O4:Eu2+,Dy3+ and Gd2O2S:Pr3+ was undertaken with a view to optimize their synthesis methods. To investigate thecrystallinity, particle size, efficiency and homogeneity in doping of Mn in ZnS; Eu and Dy inSrAl2O4 andPr in Gd2O2S, analytical techniques such as XRD, TEM, PL, TOF-SIMS and laser-SNMS wereemployed. The XRD and TEM studies revealed the average particle sizes to be between 2and 15 nm. Photoluminescence (PL) studies carried out for the nanophosphors confirm theeffectiveness of doping in the host lattices. TOF-SIMS spectral analysis showed theformation of the crystal (host lattice) with the presence of different dopants.The chemical imaging mode of TOF-SIMS suggested homogeneous doping inZnS:Mn2+ nanophosphorwhile in the case of SrAl2O4:Eu2+, Dy3+ the degree of homogeneity of doping was found to be considerably less. The broad band of PL inSrAl2O4:Eu2+,Dy3+ nanophosphor may be attributed to such an inhomogeneity to some extent. In the case ofGd2O2S:Pr3+,the PL was found to be brightest at the higher energy region. But because of very low level doping ofPr3+ inthe Gd2O2S lattice, additional laser-SNMS studies were carried out for analysing the dopingdistribution using chemical imaging data, which indicated a high degree of homogeneity.