Formation and structure of epitaxial nickel silicide on Si{111}

A LEED (low-energy electron diffraction) study of the reaction of very thin Ni films on Si{111} suggests the existence of a threshold coverage of Ni for the formation of NiSi2. If the initial Ni coverage is 6 monolayers or less, high-temperature anneals at 900-1200°C for times of a few seconds up to a few minutes produce a 1×1 structure. The LEED spectra from this structure are practically identical to those of the quenched "1×1" phase that can be obtained by quenching from high to room temperature the 1×1 phase of clean Si{111}. If the initial Ni coverage is higher than 6 monolayers then the above high-temperature anneals produce epitaxial NiSi2. The top layer of the NiSi2{111} film contains only Si atoms; the second layer contains only Ni atoms. The first interlayer spacing is contracted approximately 25% with respect to the bulk value. © 1983 The American Physical Society.