Electronic structure of the Fe/Ge(110) interface

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Abstract
Ge and bcc Fe have lattice spacings which are well matched, and therefore these elements present an excellent prototype system to study magnetic effects at a metal-semiconductor interface. We study the electronic structure of the (110) Fe/Ge interface using a parametrized tight-binding approach. The necessary tight-binding parameters were determined by fitting to first-principles band structures of Ge, spin-polarized bcc, Fe, and a CsCl-structure FeGe compound. We have implemented a generalized Slater-Koster scheme suitable to handle arbitrary atomic geometries, which allows the number of layers of each material to be increased easily to study convergence of interface properties. We find that seven layers of Fe and eleven layers of Ge are necessary to identify unambiguously the interface bands in this system. The Fe minority-spin projected band structure has a large gap around the M¯ point which spans the fundamental gap in Ge; there are eight interface bands which lie in this mutual gap. For the majority-spin electrons we also find a large density of interface resonances just above the Fermi level which are strongly localized on the Ge atoms at the interface. These results are consistent with the reactive nature of this interface seen in experimental studies.