The scanning tunneling microscope is used to image properties of the buried NiSi2/Si(111) Metal-semiconductor interface using electron interferometry. This technique reveals the presence of multiple domains in conductance images that are not visible in topographic images. The multiple domains are explained in terms of silicide regions of different thicknesses that are separated by step domain boundaries at the buried interface. The possible influence of these extrinsic defects on the formation of the Schottky barrier and on local real space characterization techniques used to measure Schottky barrier heights are discussed.