Fe/Bi superlattices: Fabrication of thin films and their characterizations

Iron and bismuth are known to be immiscible and unable to chemically bond with each other. Recent success in use of high-pressure techniques to synthesize FeBi₂ under high pressure and temperature has inspired many to ask what physical properties it would possess. In this spirit, we have prepared Fe/Bi superlattice by e-beam evaporation to form thin film heterostructures with alternating Fe/Bi bilayers of various thicknesses and individual layer thickness ratios. The interfaces are expected to be smooth and sharp because of the immiscibility, though such simple expectation may have overlooked the surface or interface energy factors that would bear consequences on the uncertainty of crystallographic anisotropy. In this work, the bismuth and iron layers are grown with different sequences or on different substrates or substrate orientations. The physical properties are investigated in order to understand the coupling effects of the heterostructures in correlation to material structures. First-principle calculations were conducted to assist the data interpretations from the perspective of electronic structures.