PHOTOLUMINESCENCE AND PHOTOINDUCED CHARGE-TRANSFER IN KTAO3-CR,LI

Kinetics and spectral composition of the luminescence of a KTaO3:0.1%C r,10%Li sample (molar charge percentages) have been studied within a b road temperature range (2-300 K). The luminescence spectra of KTaO3:O. 1%Cr,10%Li have been found to have a strong narrow R-line characterist ic of Cr3+ ions, with a clearly pronounced vibronic wing. Whereas the R-line width in Li-codoped samples is only higher by 120% than that of crystals doped only with chromium, the R-luminescence intensity in th e presence of lithium increases by several orders of magnitude. It is shown that the luminescence excitation, besides the intracenter mechan ism, is dominated by a process involving photoinduced charge transfer, which results in specific kinetics of the photoluminescence. The lumi nescence excitation model considered in the work is based, in particul ar, on the substantial role played in this process by electronic polar on capture by the Li+ dipole center caused by the existence of a chara cteristic shallow electron trap. (C) 1997 American Institute of Physic s.