Cobalt adsorption on the bare Si(100) 2 × 1 surface at low temperature (12 K)

The adsorption of Co atoms on the bare Si(100)-2 × 1 surface at low temperature (12 K) is performed in the low coverage regime (< 0.1 monolayer). The ensuing surface is studied by means of a low temperature (9 K) scanning tunneling microscope (STM). Several adsorption sites are described via STM topographies and differential conductance spectroscopy. Our study reveals that at low temperature (12 K), a significant fraction of the Co atoms diffuse into the surface and form the first stage reaction sites that are relevant for the silicidation mechanism of the Si(100). Furthermore, the low temperature conditions allow to describe surface Co adatoms conformations that are stabilized on the Si(100)-c(4 × 2) surface. Interestingly, we have observed the irreversible transformation of the symmetric pedestal site (Ps) to the under dimer site (UD) via specific STM scanning conditions. Finally, the presence of dimer vacancy lines is discussed and reveals that the activated etching process of the silicon dimer with metals can be induced at very low temperature.