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

Abstract

In this work, we investigate the impact of annealing temperature (320–700 °C), Ni salt concentration in the Ni-doped precursor 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 reveal that, after 2 h of thermal annealing at temperatures above 380 °C, the nanoplates exhibit similar average diameters (∼80 nm) and thicknesses (∼1.8 nm) across all samples, independent of annealing temperature and Ni concentration. We attribute this apparent size self-regulation to strain accumulation at the Si/NiSi2 interface arising from lattice mismatch and/or to the limited extent of stacking-fault edges that serve as preferential nucleation sites. Furthermore, repeated deposition cycles increase the nanoplate density linearly up to eight cycles, beyond which etching-driven SiO2 removal leads to a decrease in their number.