Effect of Fe/Si ratio on epitaxial growth of Fe₃Si on Ge substrate

The effects of the Fe/Si ratios on molecular beam epitaxy (MBE) of Fe ₃Si on Ge substrate have been investigated in a wide range of growth temperatures (60-300°C), From XRD measurements, it was found that Fe ₃Si layers were epitaxially grown on Ge(111) substrates at 60-200°C under the stoichiometric (Fe/Si ratio of Fe:Si=3:1) and non-stoichiometric (Fe/Si ratio of Fe:Si=4:1) conditions. From RBS measurement, it was found that atomic mixing of Fe and Ge at Fe₃Si/Ge interfaces began at a growth temperature of 300°C. In the case of MBE under the stoichiometric condition (Fe:Si=3:1), the crystallinity of Fe₃Si is significantly improved compared to the non-stoichiometric condition (Fe:Si=4:1). As a result, very low χ_min was obtained in a wide temperature (60-200°C) under the stoichiometric condition. From the transmission electron microscopy measurements, it was shown that high-quality DO3-type Fe₃Si/Ge structures with atomically flat interfaces were realized at a low temperature (∼200°C) under the stoichiometric condition.