OPTICAL-PROPERTIES OF VANADIUM IONS IN ZNSE

The photoluminescence of intentionally vanadium-doped ZnSe crystals displays at low temperatures (T almost-equal-to 4 K) the emission of the V3+ (d2), V2+ (d3) and V+ (d4) ions with different no-phonon structures at 5440, 4740 and 3640 cm-1, respectively. The excitation spectra of the V3+ and V2+ luminescence bands are investigated separately and exhibit structures of the respective spin-allowed as well as spin-forbidden internal transitions, which are largely in accordance with those of ZnS:V The corresponding energy levels are approximated in a computation following the Tanabe-Sugano scheme. Furthermore, charge transfer processes at the luminescent centres are manifest in excitation, stimulation and transmission spectra. The vanadium ion proves to be an amphoteric impurity. Commencing from V2+, the state with neutral effective charge, light-induced transitions of donor and acceptor type are disclosed: V2+ <-- --> V3+ + e(CB)- and V2+ <-- --> V+ + e(VB)+