Optically detected magnetic resonance studied via the blue luminescence of Ti-doped Al2O3
|CHARGE-EXCHANGE PROCESSES; ELECTRON-SPIN-RESONANCE; EMISSION; Physics; Physics, Condensed Matter; SAPPHIRE CRYSTALS; SPECTROSCOPY
|IOP PUBLISHING LTD
|JOURNAL OF PHYSICS-CONDENSED MATTER
The UV-excited blue and green luminescence bands of Ti:sapphire are characterized by ODMR. These emission bands are attributed to two Ti3+-O- centres, which show very similar properties and are created as a result of a charge-transfer transition of an electron from O2- to Ti4+ ions. In both centres, the d electron of Ti3+ and the hole of O- are strongly coupled and form tripler states. Doubler systems can be ruled out as sources of the blue-green luminescence. The angular dependence of the ODMR can be explained with an appropriate spin Hamiltonian assuming orthorhombic local symmetry. The orientation of the principal axes of the g-tensor and the crystal-field tensor, found for both centres, suggest that the hole is localized on a single oxygen ion and that the Ti3+-O- bond is almost aligned with the Al-O bonds of the undisturbed lattice.
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