Controlled growth of Co nanofilms on Si(100) by ion-beam deposition

This paper examines the effect of ion-beam sputtering conditions on the nucleation of Co nanofilms on Si(100). The argon ion energy is shown to play a key role in determining the sputtering process. Sputtering a cobalt target with argon ions less than 0.8 keV in energy produces granular layers. The cobalt layers grown at Ar⁺ ion energies above 1.2 keV are continuous even in the nucleation stage. The layers 1.2 to 2 nm in thickness have high resistivity and are comparable in magnetic properties to bulk material. The high-energy component of the total flux of cobalt atoms ejected from the target plays an important role in the initial stages of deposition, especially at argon ion energies from 1.2 to 2.2 keV. In the nucleation stage, the cobalt atoms have a finite penetration depth in the silicon substrate, where they give up energy which facilitates the formation of a continuous layer in the initial stage of the process.