Formation conditions and atomic structure of the Si(111)-√19 Ni surface

We determined the formation conditions and atomic structure of the Si(111)-√19 Ni surface using Auger electron spectroscopy, reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The √19 phase can be produced by low temperature deposition followed by annealing and quenching from above 860°C. It tends to coexist with a variable density 1 × 1-RC (ring cluster) phase. The intrinsic coverage of the √19 phase alone is approximately 0.15 monolayers, corresponding to three Ni atoms per √19 unit cell. Deposition at 550°C suppresses the 1 × 1-RC phase and creates a well-ordered √19 phase in coexistence with Si 7 × 7. Deposition at 350°C produces silicide islands in a matrix of Si 7 × 7. From high resolution STM images we determined the lattice registration of the √19 phase and present a model for its atomic structure.