A capacitance-spectroscopy technique based on accurate phase detection has been developed to measure the unoccupied states at silicide-silicon contacts. For Pd and Ni silicides, a dispersed group of states was found to exist in the Si band gap with its peak at a level 0.63–0.65 eV above the valence-band edge. Silicide formation alters their density and distribution to reflect the changes in the structural perfection and barrier height. Observations on the epitaxial ${\mathrm{NiSi}}_2$-Si(111) interfaces reveal that the characteristics of these states are controlled by the degree of structural perfection of the interface instead of the specific epitaxy. This seems to be the first correlation of the structural and electronic properties of a silicide-silicon interface.

• Received 9 May 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.177