Disordering kinetics in monocrystalline and epitaxial Si upon energy deposition induced by dual-beam ion irradiation

Abstract

In this work, the effect on the amorphization process of the simultaneous electronic (S_e) and nuclear (S_n) energy deposition occurring upon dual-beam irradiation experiments was studied in both bulk Si single-crystals (Si-b) and epitaxial Si thin layers (Si-tl). For this purpose, 900 keV I (for S_n) and 27 MeV Fe (for S_e) ions were used at different fluences in order to get complete disordering kinetics. These latter were determined through the monitoring of both the disorder fraction, obtained via Rutherford backscattering spectrometry in channeling experiments and the elastic strain derived from X-ray diffraction measurements. Raman spectroscopy 2D-maps were also recorded to support the results of the two other techniques. RBS/C data indicate that S_n irradiation alone leads to full amorphization of the irradiated region in both Si-b and Si-tl at a fluence of 1.5 × 10¹⁴ cm⁻². In contrast, during the dual-beam irradiation (S_n & S_e), such a complete phase transformation is prevented up to a fluence of 3 × 10¹⁴ cm⁻². Similarly, the maximum elastic strain developing before the loss of crystallinity reaches a maximum of ~ 1% at 1.5 × 10¹⁴ cm⁻², but it remains below 0.2% at the same fluence in the S_n & S_e regime for which full amorphization is not detected. These results indicate that the electronic energy deposition induces a significant dynamic annealing of the damage created by the nuclear energy loss, and this annealing occurs over the entire investigated fluence range (i.e., up to 3 × 10¹⁴ cm⁻²). The annealing efficiency is shown to be lower for Si-tl, as demonstrated by the disorder and strain values that are always larger than for the bulk counterpart.