Evidence of V- centers in trivalent rare-earth doped MgS.

Abstract

A thermoluminescence (TL) peak near 80 \ifmmode^\circ\else\textdegree\fi{}C is observed in MgS singly doped with a different trivalent rare-earth ion (${\mathrm{Sm}}^{3+}$, ${\mathrm{Ce}}^{3+}$, ${\mathrm{Tb}}^{3+}$) and exposed to ionizing radiation at room temperature. It appears that the ${V}^{\mathrm{\ensuremath{-}}}$ center, as in alkaline-earth oxides, is the origin of the TL peak. A suggested mechanism of charge trapping to explain the observed results is that the electrons are trapped at the trivalent ions and the holes at the vacancies. On heating the sample over 100 \ifmmode^\circ\else\textdegree\fi{}C, thermal destructions of the ${V}^{\mathrm{\ensuremath{-}}}$ centers occur, and the released holes recombine with the trapped electrons at the ${\mathrm{Sm}}^{3+}$ (${\mathrm{Ce}}^{3+}$, ${\mathrm{Tb}}^{3+}$) ions, leading to the luminescence that is characteristic of ${\mathrm{Sm}}^{3+}$ (${\mathrm{Ce}}^{3+}$, ${\mathrm{Tb}}^{3+}$) ions.