Formation and magnetic properties of the silicon-cobalt interface

Formation of the Si/Co interface and its magnetic properties have been studied by high-resolution photoelectron spectroscopy with synchrotron radiation. The experiments have been performed in situ in superhigh vacuum (5 $\times$ 10$^{-10}$ Torr) with coating thicknesses up to 2 nm. It has been found that, in the initial stage of silicon deposition on the surface of polycrystalline cobalt maintained at room temperature, ultrathin layers of the Co$_3$Si, Co$_2$Si, CoSi, and CoSi$_2$ silicides are formed. The three last phases are nonmagnetic, and their formation gives rise to fast decay of magnetic linear dichroism in photoemission of Co 3$p$ electrons. At deposition doses in excess of $\sim$0.4 nm Si, a film of amorphous silicon grows on the sample surface. It has been established that the Si/Co interphase boundary is stable at temperatures up to $\sim$250$^\circ$C and that further heating of the sample brings about escape of amorphous silicon from the sample surface and initiates processes involving silicide formation.