Nanostructure of near-surface Si layers formed by implantation and pulsed laser annealing

A Si single crystal was implanted with a 5·1015 cm-2 dose of 80 keV Si ions. We report the results of experimental and theoretical investigations of the structural changes induced by ultraviolet laser pulse in this crystal. The structural changes in the near-surface region were examined by means of reflection high-energy electron diffraction, Rutherford backscattering and interference-polarizing Nomarski microscopy. Numerical calculations of transient temperature profiles in the irradiated target were performed in order to evaluate the threshold and the optimal value of the radiation energy density, and to determine the temperature profiles in the annealed region. The obtained results were compared with previous findings of a defect structure in a laser annealed Si crystal matrix implanted with Ge ions. The formation of an extended defect structure on the surface of the annealed areas where melting and solidification occur was observed. The creation of this structure is a result of the relaxation of stresses caused by inhomogeneous heating and inhomogeneous cooling of the melted near-surface layer and it is independent of the introduced dopant