A study on Si nanocrystal formation in Si-implanted SiO₂ films by x-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy are used to study Si nanocrystal formation in Si-implanted SiO₂ films as a function of thermal annealing. Analysis of the XPS Si 2p peaks shows the existence of five chemical structures corresponding to the Si oxidation states Siⁿ⁺ (n = 0, 1, 2, 3, and 4) in the SiO₂ films, and the concentration of each oxidation state is determined quantitatively. The XPS results show a clear picture of the evolution of the chemical structures and the formation of Si nanocrystals as functions of annealing temperature and annealing time. The evolution of the concentrations of the five oxidation states with annealing is explained in terms of the thermal decompositions of the suboxides corresponding to the three oxidation states Siⁿ⁺ (n = 1, 2, and 3) and the thermal oxidation of the implanted Si.