PHOTOLUMINESCENCE OF THE UNDOPED GAMMA-LN(2)S(3) AND DOPED GAMMA-[NA]LN(2)S(3) RARE-EARTH SULFIDES (LN=LA,CE)

A study of the photoluminescence of the undoped gamma-La2S3 and gamma- Ce2S3 and doped gamma-[Na]Ce2S3 rare earth sulfides, performed compara tively under steady state and time resolved excitation and detection c onditions, is reported. The higher energy emission observed under time -resolved conditions for gamma-La2S3 is assigned to a transition from the conduction band to a level located ca 0.7 eV above the valence ban d whereas the emission observed under steady state conditions is essen tially due to transitions from defect levels under the conduction band . The luminescence observed for the undoped and sodium-doped cerium su lfides is assigned to transitions from the conduction band to the Ce3 4flevels, Clearly, the luminescence observed under steady state condi tions may be separated, employing time resolved conditions, into emiss ions from the intrinsic and perturbed ions.