Metallization-induced spontaneous silicide formation at room temperature: The Fe/Si case

The composition of the interface resulting from the room-temperature deposition of iron on Si(100) under ultrahigh-vacuum conditions has been monitored by surface-sensitive techniques such as Auger electron spectroscopy, low-energy electron diffraction, and photoemission spectroscopy with synchrotron radiation. The results show unequivocally that the Fe/Si interface is not abrupt, but rather an amorphous intermixed region with composition close to ${\mathrm{Fe}}_3$Si. The formation of this silicidelike layer is related to the metallization of the deposited Fe overlayer. Upon annealing a thick film of Fe, we demonstrate that ${\mathrm{Fe}}_3$Si is the first phase to nucleate, in opposition to standard models that point to FeSi as the first silicide formed.