Structural and electronic properties of thin fluorite-structure NiSi2, COSi2 and FeSi2 interfaces and precipitates in Si

MG Wardle, JP Goss, PR Briddon and R Jones
Physica Status Solidi A

Interface geometry and electronic properties of fluorite-structure NiSi2, CoSi2 and FeSi2 layers in {111} oriented silicon are studied using density functional methods. Of the atomically flat geometries studied, NiSi2 is found to preferentially form an interface where the transition-metal atoms are 7-fold coordinated, whereas CoSi2 and γ-FeSi2 both adopt 8-fold coordinations. Schottky-barrier heights are detailed for the low energy interface structures of the three disilicides. The localisation of states introduced below the Si valence band and in the band-gap are detailed for infinite systems, with preliminary results for finite layers simulated by dislocation dipoles also being discussed. Our calculations support the view that gap-states for silicide precipitates are associated with bounding dislocations rather than the planar interfaces.

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