The incorporation site of Cu in the scintillator and thermoluminescent dosimeter material lithium tetraborate Li2B4O7:Cu was shown to depend on the charge state of the dopant. As confirmed by a refined analysis, the EPR spectra of an unpaired hole could be ascribed to Cu2+ situated near the Li lattice site with C1 symmetry, in contrast to the higher (C2) overall symmetry reported earlier for Cu+ in its relaxed excited state, the latter suggesting interstitial incorporation for the monovalent dopant. Consequences for charge transfer processes involving copper ions were considered.

Different Incorporation of Cu+ and Cu2+ in Lithium Tetraborate Single Crystals. G.Corradi, V.Nagirnyi, A.Watterich, A.Kotlov, K.Polgár: Journal of Physics - Conference Series, 2010, 249[1], 012008