Comparative first-principle analysis of un-doped and V3+-doped α-ZnAl2S4 spinel

On the excitation spectra of Cr3+/Cr2+ and V3+ co-doped ZnAl2S4 single crystals

“…In particular, energy levels of the Cr 3+ ion, as derived from the excitation spectrum, are not consistent with the Tanabe-Sugano diagram for the d 3 ions in the octahedral coordination. Another issue is related to a "missing" 3 T 1 ( 3 F) -3 T 2 ( 3 F) band in the absorption spectrum of V 3+ ions in ZnAl 2 S 4 , although this band should be present due to a spin allowed transition.…”

“…One interesting feature of vanadium ions in this crystal is that some peaks in the emission spectrum are due to the transitions between different excited levels (denoted as the PL1 in Fig.8), which is more typical for the lanthanides rather than for the transition metals ions. At room temperature the emission is due to the 3 T 2g ( 3 F) to 3 [4]. The intensity at room temperature is increased by a factor of four compared to low temperatures (see the Inset).…”

“…[4] and the theoretical calculation on the V 3+ level location within the band gap of the host material was carried out in [3]. Although the reader can find a more detailed description in the above mentioned references, we will present here a short summary of those two publications in order to emphasize what we want do describe further.…”

“…Synthetic α-ZnAl 2 S 4 single crystals doped with various transition metal ions such as Ti, Cr, Co or V have been the subject of investigations in our group in the past few years [1][2][3][4][5] due to their potential applications as optically active media for tunable laser systems. Unlike the crystals containing trivalent chromium, materials with other transition metal ions, especially in other oxidation states, are not easy to deal with.…”

“…Except for the first band in the PLE there is a perfect coincidence between this one and the absorption spectrum. The vertical bars represent the calculated levels of V 3+ in ZnAl 2 S 4[3].…”