The effect of annealing temperature, concentration of Ni salt, and number of deposition cycles on the size and density of NiSi2 nanocrystals grown from thermal activated diffusion of Ni atoms in single-crystal Si(001) wafers

In this work, we examined the effects of annealing temperature (320-700 {degree sign}C), Ni salt concentration in precursor Ni-doped thin films, and multiple deposition cycles on the morphology and density of endotaxial NiSi₂ nanoplates formed near the external surfaces of single-crystal Si(001) wafers. Grazing-incidence small-angle X-ray scattering measurements show that after two hours of thermal annealing at temperatures above 380 {degree sign}C, nanoplates exhibit a nearly constant diameter (~80 nm) and thickness (~1.8 nm), regardless of annealing temperature or Ni concentration, suggesting self-limited growth. We attribute this self-regulation to strain accumulation at the Si/NiSi2 interface due to lattice mismatch and/or to the restricted size of stacking-fault edges that act as preferential nucleation sites. Furthermore, repeated deposition cycles increase the number of nanoplates linearly up to eight cycles, after which etching-driven SiO2 removal decreases their number.