Stacking fault induced relative dipole at type-A/B NiSi sub 2 /Si(111) interfaces and its correlation to the Si(111)-7 x 7 sub-unit cell structures.

The change in electronic structure from a type-A to a type- B NiSi sub 2 /Si(111) interface is sufficient to explain the previously observed difference in the Schottky Barrier Heights of these two interfaces. This is supported by the observation by scanning tunneling microscopy of different contrast on the faulted triangle in a Si(111)-7 x 7 unit cell relative to the unfaulted one. The crystallographic differences in the two types of NiSi sub 2 /Si(111) interface are identical to those in two types of triangles inside a Si(111)-7 x 7 unit cell. A simple model with an interface dipole induced by the stacking fault is proposed to be responsible for the 0.13 eV difference in the Schottky barriers at type-B NiSi sub 2 /Si(111) interfaces relative to type-A interfaces. The estimated dipole charge is about 0.004 e- per interface bond, in good agreement with a theoretical estimation at the stacking fault of bulk Si.