Electronic excitations and luminescence in MgO : Ge single crystals

MgO single crystals, doped with Ge2+ 'mercury-like' ions, were grown. The e mission of Ge2+ centres (similar to 3.2 eV) can be efficiently excited at 4 s(2) --> 4s4p electron transitions in Ge2+ ions (4.8-6.4 eV) as well as at the formation of electron-hole (e-h) pairs by 8-36 eV photons. The absorpti on of one photon of 25 or 30 eV leads to the creation of two or three e-h p airs, respectively. The thermal quenching of the emission begins at similar to 500 K and follows the Mott law with an activation energy E = 0.52 eV. T aking advantage of the relatively high thermal stability of Ge2+ luminescen ce, high temperature thermostimulated luminescence (up to 775 K) of MgO:Ge crystals has been investigated. (C) 2000 Elsevier Science B.V. All rights r eserved.