Fe1+ transient charge state in ZnS: 57Co Mössbauer sources

Mössbauer absorption and emission experiments in CaF2(57Fe): relaxation and after-effect study

“…In order to check this point, it would be interesting to prepare CaF2 (57Co) sources by methods other than diffusion, for example by 57 Co implantation followed by a convenient annealing, and to examine whether non cubic Fe2+ Fe3 + and components are again present or not. It is to be noted that we also did not observe the presence of a Fe3 + charge state in ZnS ( 57co ) [3,4], although Fe3 + ions are often thought to be systematically observed in insulators or in semi-conductors, following the Auger cascade after the 57 Co decay.…”

“…In ZnS (57Co ) [4], the thermal variations of the second order Doppler shift and of the Debye-Waller factor are the same for the Fel ' and Fe 2, ions. The effective Debye temperature is thus found to be the same for both Fel + and Fe2+ in ZnS, and therefore the Fe1+ ions seem to belong to ZnS bulk.…”

“…The effective Debye temperature is thus found to be the same for both Fel + and Fe2+ in ZnS, and therefore the Fe1+ ions seem to belong to ZnS bulk. The abrupt disappearance of the Fe1+ single line at 255 K is attributed to the transient character of this ion in this semi-conducting matrix, with the Fel + life time becoming much smaller than the nuclear life time T. for T > 255 K. Both MES [4,19] and optical excitation measurements [20] in ZnS show that the Fe1+ ions transform into Fe2 + ions by giving an electron to the conduction band, through a 0.2 eV energy activation process.…”

“…No detailed study of the cubic site Fe2+ fraction could be made in the crystal sources Bi and B2, as the 57Co substitutional fraction was too small in these samples. 4. Emission relaxation lineshape analysis.…”

“…The energy level scheme ( Fig. 1) of the substitutional Fe 2, ions is of the same type as in the fourfold coordinated sites in the cubic ZnS matrix, where we have already performed a similar double MAS-MES study [3,4]. Two interesting differences however exist between these two matrices.…”