Mössbauer Studies of Implanted Ions in Semiconductors

Abstract

The method of radioactive ion implantation for studying the location of impurities in semiconductors is discussed. Mossbauer measurements in semiconductors are reviewed with special emphasis on the case of Te129m ions implanted into single crystals of silicon, germanium and diamond as well as in several alkalide halides. The spectra of all semiconducting sources display two well separated MOssbauer lines of comparable intensity. The positions, widths and relative intensities of the lines are found to depend only slightly on annealing and on dose. No dependence on the dope already present in the semiconductors has been observed. The results obtained for I129 in these semiconductors are compared with data obtained at Stanford with Fe57 implanted in semiconductors by recoil, using a Van de Graaff accelerator. The separation of the lines of the I129 sources is observed to be proportional to that of the Fe57 sources. On the basis of the systematics of I129 isomer shifts, the line with negative isomer shift (decreased s-density) is tentatively assigned to be due to iodine atoms in substitutional sites, that with positive shift to atoms at interstitial sites. The nature of the interaction causing the very large shifts is discussed.