Electron trapping centres and cross sections in LiNbO3 studied by Co-57 Mossbauer emission spectroscopy

Fast electron trapping processes and aliovalent charge states following the Co-57(EC)Fe-57 decay are studied in undoped, 5.4 mol% Mg-doped and 0.1 mol % Fe-doped LiNbO3 in various thermochemical reduction (TCR) states. Static Co-57 Mossbauer emission spectra of congruent Mg:LiNbO3 recorded at T = 4.2 K in external magnetic field of 4.6 T are presented. Trapping cross sectio n ratios are derived for Fe-Li(3+), Nb-Li(5+) and Mg-Li(2+). A method to de termine trap concentrations for TCR states of LiNbO3 is outlined. The elect ron-capture distance of the traps is found to be 2.7 +/- 1.4 nm. As this is much smaller than the 6 keV Auger-electron penetration depth, it is conclu ded that the distribution of the aliovalent charge states at 4.2 K is deter mined mainly by the 600 eV Auger electrons.