The effect of high iron-ion implantation doses on the X-ray emission spectra of silicon

X-ray emission spectroscopy (Si L _{2, 3} spectra, 3d3s → 2p electronic transition) was employed to study p-and n-type silicon samples implanted with Fe⁺ ions in a pulse mode (the implantation energy was 30 keV, the pulse current was varied up to 0.5 A, the pulse duration was 400 µs, and the ion irradiation doses ranged from 10¹⁴ to 10¹⁷ cm^?2). The x-ray emission spectra were found to be dependent on the ion irradiation dose and the electron-accelerating voltage that was used in the x-ray studies. By comparing the Si L spectra with the spectra of reference materials and by modeling the former spectra, it was revealed that, as the ion-irradiation dose increases, there occur disordering of the structure, partial amorphization of the sample in a surface layer approximately 7200-Å thick, and its subsequent recrystallization (under high irradiation doses). It was shown that this effect is most pronounced in a layer at a depth of ～1000 Å and is not associated with the formation of iron silicide FeSi in the bulk of the sample but rather is due to the breakage of Si-Si bonds caused by ion implantation under the irradiation doses used.