Study of structure and optical properties of β-FeSi 2 precipitates formed by ion-implantation of Fe + in Si(100) and effects of co-implantation of Fe + and Si + in amorphous SiO 2

Abstract

Fe + ions were implanted in Si(100) and subsequently annealed. The samples were characterised by Rutherford backscattering spectrometry (RBS), transmission electron microscope (TEM), transmission electron diffraction (TED), photothermal deflection spectroscopy (PDS), and photoluminescence (PL). Formation of β-FeSi 2 precipitates in Si after annealing at 850°C and their specific orientation of 〈202〉β∣∣〈111〉Si and 〈010〉β∣∣〈011〉Si were confirmed by TEM. A weak optical absorption above 0.8 eV corresponding to the band-gap of β-FeSi 2 was detected by PDS, and a broad PL at 0.8 eV was also observed. The intensity of this PL line was enhanced remarkably with additional annealing at the same temperature in a H 2 atmosphere. However, a number of defects were produced in the near surface region by ion-implantation. Since defects from PL were produced, in particular originating from dislocations in Si, is also located at approximately 0.8 eV, the origin of the PL is still uncertain. In order to eliminate the PL from dislocations in Si, a formation method of β-FeSi 2 precipitates in SiO 2 films on Si was tried by co-implantation of Fe + and Si + ions with a dose at the stoichiometrical ratio of 1:2. However, part of implanted Fe diffused out from the implanted region after annealing. Thus, co-implantation of both Fe + and Si + ions in SiO 2 is not an appropriate way to form β-FeSi 2 precipitates in SiO 2.