The Y–Si(111) interface formation studied by scanning tunneling microscopy

We have investigated the formation of the Y–Si(111) interface at room temperature by the scanning tunneling microscopy (STM) technique. The nucleation of the yttrium is localized to the inner part of every subunit cell of the (7×7) reconstruction. Thus, small silicide-like amorphous islands are formed by reaction of the yttrium atoms with the adatoms and dangling bonds of the rest atoms. By analyzing the voltage dependence of the STM images we have concluded that these nuclei present a semiconducting behavior. For coverages around one monolayer the nuclei coalesce, conferring a metallic character to the interface.