Unstable isotopes of 57Mn (half-life of 105s) were separated and implanted into FZ– and CZ–Si wafers using a RIKEN projectile nuclear fragment separator (RIPS). Subsequently, Mössbauer spectra of 57Fe in Si were measured at up to 800K, in order to study the charge states and the diffusion processes of interstitial and substitutional Fe atoms in Si matrix. The spectra consist of two singlets between 300 and 650K, and only one singlet above 700K. The isomer shifts of the singlets at 300K were 0.809 and −0.042mm/s, referred to the value of α-Fe. The values correspond to interstitial and substitutional Fe, respectively. Above 600K, both the disappearance of the interstitial component and the simultaneous relaxation effects on the centre shifts were clearly observed. These dynamical behaviours could be interpreted as a reaction process of interstitial Fe atoms jumping into vacancies, which were accompanied by changes in the charge states. Above 650K, a line-broadening of the singlet could be also seen, indicating an enhanced diffusion of the Fe atoms due to the excess vacancies.

In situ Observation of Substitutional and Interstitial Fe Atoms in Si after GeV-Implantation - an In-Beam Mössbauer Study. Y.Yoshida, Y.Kobayashi, K.Hayakawa, K.Yukihira, A.Yoshida, H.Ueno, F.Shimura, F.Ambe: Physica B, 2006, 376-377, 69-72