Solid phase crystallization of amorphous Fe–Si layers synthesized by ion implantation

Abstract

Microstructural changes of ion-beam-synthesized amorphous Fe–Si layers on thermal annealing were investigated using transmission electron microscopy. Single crystal Si(111) substrates were irradiated with 120keV Fe+ ions at cryogenic temperature to a fluence of 4.0×1017cm−2, followed by thermal annealing at 200–700°C. The amorphous Fe–Si layer in the as-implanted sample crystallized to polycrystalline ε-FeSi and β-FeSi2 layers after annealing at 500°C for 2h.ε-FeSi transformed into β-FeSi2 and the β-FeSi2 region extended with increasing annealing temperature. Excess Fe atoms from ε-to-β phase transformation migrate toward the Si substrate via β-FeSi2 grain boundaries. We discuss the recrystallization process of amorphous Fe–Si thin layers and the growth mechanism of β-FeSi2 thin layers formed in high-dose Fe ion-implanted Si.