Mechanism of ion-induced mixing phenomena in Gold-Nickel bilayer on Si substrate

Gold/Nickel bilayer thin films deposited on Si(100) substrates are bombarded by 100 keV Ar-40(+), 260 and 300 keV Kr-84(2+) and 400 keV Xe-132(3+) ions which deposit maximum energy across the Gold/Nickel interface and hence produce maximum atomic transport within two sides of the interface. However, due to the energy of the projectile ions some Si atoms have also gained energy, which, in turn, displaces the atoms. The atomic displacements caused by the projectile in the system has been analyzed using RBS, XRD, SEM/EDS and AFM/MFM techniques. The relative change in the variance of the intermixed region across the Au-Ni-Si interfaces excluding the irradiation-induced surface roughness has been calculated and it was observed that it increases linearly with ion fluence. The measured athermal mixing rates which vary between 3.7 and 6.9 nm(4), have been explained by various existing phenomenological models. It shows that local or global thermal spike models are most suitable for explaining the ion beam-induced mixing of systems with strong thermochemical properties of the constituents. The mixing efficiency of this system has been calculated and found to be 1.2 nm(5)/keV.