Amorphous-crystal silicon interfaces: structure and movement under ion beam irradiation

Abstract

Our recent work on the kinetics of the crystal Si/amorphous Si (c-Si/a-Si) interface motion induced by energetic ion beam irradiation is reported. Ion beam irradiation may result in either epitaxial crystallization or planar layer-by-layer amorphization depending on the substrate temperature. In both cases the interface motion has been characterized by in situ reflectivity measurements and by ex situ Rutherford backscattering and channeling. At temperatures ⩾ 150°C crystallization occurs. In this regime the interface motion depends linearly on the energy deposited into elastic collisions by the impinging ions, is ∼ 4 times faster onto 〈100〉 than onto 〈111〉 oriented substrates and is influenced by the presence of impurities at the c-a interface. As soon as the temperature is lowered below 150°C the interface motion is reversed and amorphization occurs. In this regime both substrate orientation and impurities have a negligible effect on the kinetics of the process. The data will be discussed and analyzed in terms of a phenomenological model in which competitive processes between defect generation and annihilation at the c-a interface determine the evolution of the transition.