Evidence of enhanced epitaxial crystallization at low temperature by inelastic electronic scattering of mega-electron-volt heavy-ion-beam irradiation

The inelastic electronic scattering of 84Kr at energies of 0.5–5 MeV and 131,132Xe ions at energies of 1–5 MeV is directly confirmed to play a role in the ion-beam-induced epitaxial crystallization (IBIEC) of amorphous Si layers on crystalline Si substrates at 310–450 °C. The crystallization rate per unit vacancy (normalized crystallization rate) created by the elastic nuclear scattering of the incident ion beam at the amorphous–crystalline (a/c) interface is increased 40%–50% by increasing the inelastic electronic scattering three- to fourfold while maintaining the same elastic nuclear scattering conditions at the a/c interface. This normalized crystallization rate also increases with the inelastic electronic scattering at the a/c interface. However, the percentage of increase falls to about 20% as the absolute value of the inelastic electronic energy loss at the a/c interface decreases to below about 20 keV/ion/(20 nm) or as the number of vacancies created at the a/c interface increases to more than 250/ion/(20 nm). At 310–450 °C the activation energy for IBIEC induced by Kr or Xe irradiation is 0.5–0.6 eV. This value slightly larger than the 0.2–0.3 eV reported for temperatures below 300 °C reflects the thermally activated solid-phase epitaxy. The mechanism of this enhanced crystallization by inelastic electronic scattering is discussed qualitatively.