Electron paramagnetic resonance of divalent thallium in cadmium telluride

Abstract

An analysis of EPR spectra from CdTe:Tl single crystals shows that ${\mathrm{Tl}}^{2+}$ goes into the CdTe lattice as a substitutional impurity at a cadmium site. The unpaired $s$ electron on the thallium ion has an isotropic hyperfine interaction of 53.3 \ifmmode\pm\else\textpm\fi{} 0.3 and 53.7 \ifmmode\pm\else\textpm\fi{} 0.3 GHz with the $^{203}\mathrm{Tl}$ and $^{205}\mathrm{Tl}$ isotopes, respectively, and a $g$ factor of -2.035 \ifmmode\pm\else\textpm\fi{} 0.015. The sign of the hyperfine-interaction constant is inferred to be positive from the temperature dependence of the line intensities and the negative sign of the $g$ factor is assumed. A superhyperfine (shf) interaction with the nearest-neighbor tellurium ligand ions is observed whenever the sites are occupied by the 7% abundant $^{125}\mathrm{Te}$ nucleus. The shf-interaction tensor is axially symmetric about the bond direction with $|{A}_{\ensuremath{\parallel}}|=375\ifmmode\pm\else\textpm\fi{}5$ G and $|{A}_{\ensuremath{\perp}}|=180\ifmmode\pm\else\textpm\fi{}5$ G.