Electron paramagnetic resonance of divalent thallium in cadmium telluride

An analysis of EPR spectra from CdTe:Tl single crystals shows that Tl²⁺ 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 ±{} 0.3 and 53.7 ±{} 0.3 GHz with the ²⁰³Tl and ²⁰⁵Tl isotopes, respectively, and a g factor of -2.035 ±{} 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 ¹²⁵Te nucleus. The shf-interaction tensor is axially symmetric about the bond direction with |A_∥|=375±5 G and |A_⊥|=180±5 G.