アイテム詳細

要旨

In low-temperature photoluminescence (PL) of Ti-doped ZnTe crystals, three zero­ phonon lines (ZPL) show up at 3903, 4013, and 4103 ^cm-1. By Zeeman measurements the line at 3903^cm-1 is identified with the ²T₂(D)→²E(D) transition of substitutional Ti³⁺ (3d¹). The weak ³T₂(F)→³A₂(F) band of Ti²⁺ (³d₂) exhibits a single ZPL at 2855^cm-1. Magnetooptic spectra display a threefold splitting of the isotropic Ti²⁺ line and a further splitting of the Ti³⁺ lines. In Ni co-doped crystals the known PL bands of Ni²⁺ (3d⁸ at 3840^cm-1 and Ni⁺ (3d⁹) at 3095^cm-1 occur in addition. While after cooling these crystals in the dark, only the luminescence of Ti³⁺ is observed, the Ti²⁺ emission appears after irradiation with light (̅v>7000^cm-1): Ti ³⁺+ hv→ Ti²⁺+e⁺_VB. This charge transfer (CT) is confirmed by electron paramagnetic resonance (EPR) investi­gations. Under irradiation, the isotropic signal of Ti³⁺ at g=1.9139 present in thermal equilibrium at 4 K, is reduced in favour of the photo-stimulated Ti²⁺ signal at g=1.9255. Excitation and sensitisation processes are discussed in one-particle models comprising the involved ionisation states of Ti.