Springer LINK: The European Physical Journal B - Abstract Volume 4 Issue 3 (1998) pp 269-277

The European Physical Journal B

ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)

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Abstract Volume 4 Issue 3 (1998) pp 269-277

Optical and paramagnetic properties of titanium centres in ZnS

J. Dziesiaty (1), M.U. Lehr (2), P. Peka (2), A. Klimakow (1), S. Müller (1), H.-J. Schulz (2) (a)

(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

Received: 3 October 1997 / Revised: 17 December 1998 / Accepted: 18 May 1998

Abstract: ZnS:Ti crystals grown by different methods are investigated at low temperatures (2 K $\leq T \leq 80$ 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 Ti²⁺(d²) 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 $^3T_2(F) \rightarrow{}^3A_2(F)$ 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 ³T₁(F) and ³T₁(P) bands in excitation spectra. Substitutional Ti³⁺(d¹) is identified by an anisotropic EPR spectrum at T = 3.5 K, indicating a quasistatic Jahn-Teller effect at the doubly degenerate ²E(D) ground state, while in the first excited vibronic state a quasidynamic JT effect in the strain-split vibronic ²E/²A₂ 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 $^2T_2(D) \rightarrow{}^2E(D)$ 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.

PACS. 71.70.-d Level splitting and interactions- 76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)- 78.55.Et II-VI semiconductors

(a) email: schulz@fhi-berlin.mpg.de

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