Structural and electronic property evolution of nickel and nickel silicide thin films on Si(100) from multicore x-ray-absorption fine-structure studies

We report an x-ray-absorption fine-structures (XAFS) investigation of a series of nickel and nickel silicide thin films prepared by magnetron sputtering nickel on Si(100) substrates and sequential annealing procedures. XAFS at the Ni K edge, Si K edge, and Si L3,2 edge have been used to monitor the structure and bonding systematics at different stages of the silicidation process. It is found that the as-deposited film exhibits noticeable intermixing at the Ni-Si interface at room temperature, leading to the formation of a Ni-rich silicide in the vicinity of the interface; as the annealing temperature increases, predominantly NiSi and NiSi₂ phases are sequentially formed. It is also shown that Si L3,2-edge studies using total electron yield and fluorescence yield are ideally suited for noninvasive characterization of silicide thin films.