IMAGING DEFECT FORMATION IN THE TEMPLATE GROWTH OF NISI2 SI(111) - ANAPPLICATION OF QUANTUM-SIZE MICROSCOPY/

The tunneling microscope is used to study the solid phase reaction of thin nickel films on silicon substrates to form epitaxial nickel disil icide. The initially flat Si(111)-7 X 7 substrate develops defects in the form of surface and interface steps as the silicide reaction proce eds, with the steps corresponding to domains of NiSi2(111) of varying thicknesses. For low-temperature growth, the nickel disilicide terrace s are atomically flat, whereas below the surface there is substantial inhomogeneity. Annealing this surface to higher temperature reduces th e subsurface inhomogeneity by diffusing residual silicon to the surfac e to form adatom islands, trading off volume defects for surface defec ts. We present resonant tunneling spectra for the resulting vacuum-met al-semiconductor quantum-well structure, and discuss the conditions un der which quantum size effects occur for carriers within the thin NiSi 2 metallic film.