Chemisorption processes of transition metals Ti, Cr, and Fe on a Si(111) surface

The chemisorption of transition-metal atoms on the Si surface is of considerable importance in silicide formation. Many experimental studies have indicated quite different formation processes for refractory transition metals and near-noble transition metals. Some studies of the growth of titanium on clean silicon surfaces have led to controversial results as to the reactivity of the interface at room temperature. The authors present theoretical studies on forces acting on metal atoms (Ti, Cr, Fe) in the ${\mathrm{Si}}_6$ ${\mathrm{H}}_9$ system by using the self-consistent linear combination of atomic orbitals Xα force method. Results show that the Ti atom has a higher barrier at the surface than the Cr atom. The Ti atom tends to break the Si—Si bond rather more strongly than Cr and Fe atoms do. These behaviors are consistent with recent experimental results. The bonding properties between adatoms and the substrate were analyzed to explain the different force behaviors among transition metals.