Structure and evolution of the displacement field in hydrogen-implanted silicon

Hydrogen implantation into silicon at room temperature and at 77 K has been studied by secondary-ion mass spectrometry (SIMS), elastic recoil diffusion analysis (ERDA), Rutherford backscattering spectroscopy (RBS), multiple-crystal x-ray diffraction (XRD), conventional and high-resolution transmission electron microscopy (TEM and HREM), and binary-collision simulation (m a r l o w e). The implantation energy was 15.5 keV, low enough not to form dense collisional cascades; the fluence range was ${10}^{14}$ to 2×${10}^{16}$ ${\mathrm{cm}}^{\mathrm{-}2}$. Annealing experiments were carried out by heating the implanted samples for 2 h in the temperature interval 400–800 °C. While the hydrogen profile is well described by m a r l o w e simulation, the resulting crystal deformation, measured by RBS, XRD, TEM, and HREM, cannot be interpreted in terms of damage imparted to the silicon target, but is mainly related to the displacement field around hydrogen. An accurate analysis is, however, able to separate the contributions due to self-interstitials from that due to hydrogen. The threshold energy for Frenkel-pair production is determined and is found to be 43±5 eV, remarkably higher than the commonly accepted value of 15 eV.