Mössbauer investigation of silicide phases at the reactive Fe/Si interface

Silicide phases formed upon pulsed laser deposition of 1–60Åof Fe onto a H-terminated Si(111) surface at room temperature have been investigated by conversion electron Mössbauer spectroscopy. An interface phase with two different Fe sites of low local symmetry is formed initially with up to 8Åof Fe. For larger coverage an α-Fe phase with incorporated Si occurs. The evolution of this structure upon isothermal annealing at 250°C shows that a c-FeSi phase with B2 structure is formed first, which at later times transforms to the bulk stable ε-FeSi phase. For 60Åcoverage a Fe3Si phase is found in addition. A model for the phase formation and evolution mechanisms is proposed.