Simulation analysis of ion channeling spectra:Thermal vibrational amplitude in Si

Energy spectra for 1 MeV He ions scattered by a Si single crystal over an angle of 58-degrees were measured for incident directions along the string and a number of directions 4-degrees off the string: {100}, {110} and {111} planes as well as three non-channeling directions. The measurements were performed at a temperature of 164 K, under glancing-exit-angle conditions. The experimental spectra were reproduced by Monte Carlo simulation, and a chi(2) analysis procedure was developed to determine the thermal vibrational amplitude in Si. Two ion-atom potentials used in the calculations (the ZBL potential and a Hartree-Fock potential) yielded essentially the same amplitude of 0.066(2) angstrom. The corresponding Debye temperature of 490(15) K agrees well with recent determinations by other methods.