Eur. Phys. J. B 4, 269-277 (1998)
https://doi.org/10.1007/s100510050379

Optical and paramagnetic properties of titanium centres in ZnS

¹ Humboldt-Universität zu Berlin, Institut für Physik, Invalidenstrasse 110, 10099 Berlin, Germany
² Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

Corresponding author: ^a schulz@fhi-berlin.mpg.de

Received: 3 October 1997
Revised: 17 December 1998
Accepted: 18 May 1998
Published online: 15 August 1998

Abstract

ZnS:Ti crystals grown by different methods are investigated at low temperatures (2 K K) by electron paramagnetic resonance (EPR) and optical spectroscopies, mainly with regard to their photoluminescence properties, including excitation and sensitisation spectra. The more familiar lattice-neutral Ti ion on a cubic site (AN) presents an isotropic EPR signal with g=1.928 observable up to 80 K. Signals of axial PN and AS sites are detected in the same temperature range. This Ti²⁺ ion exhibits the transition in emission, structured by no-phonon lines (NPL) of centres in various environments, with the AN site represented at 3613 cm^-1, and the and bands in excitation spectra. Substitutional Ti is identified by an anisotropic EPR spectrum at T = 3.5 K, indicating a quasistatic Jahn-Teller effect at the doubly degenerate ground state, while in the first excited vibronic state a quasidynamic JT effect in the strain-split vibronic manifold is found. A new luminescence band centred at 4500 cm^-1 with NPL structures near 5000 cm^-1 represents AN, PN and AS sites in the transition. Charge-transfer processes are described in a one-particle model, depicting the Ti³⁺/Ti²⁺ donor level at 12 900 cm^-1 below the conduction-band edge.