Low temperature oxidation of amorphous silicon nanoparticles

The oxide layer is important for the processing and applications of silicon nanoparticles as it provides chemical stability to the material. Herein, the thermal oxidation of sub-10-nm crystalline and amorphous silicon particles in dry air is investigated with nonisothermal kinetic analysis including Kissinger and Flynn-Wall-Ozawa methods at various heating rates. The results indicate that amorphous silicon nanoparticles have a considerably lower activation energy for oxidation (98 kJ/mol) compared to their crystalline counterparts (182 kJ/mol). In situ heating diffuse reflectance infrared Fourier transform spectroscopy was employed to monitor the evolution of surface species of Si nanoparticles during oxidation. The results suggest that backbond oxidation of higher hydrides contribute to the low onset temperature for oxidation of amorphous silicon nanoparticles. Besides, surface O3Si-H and Si-OH species likely prevent the formation of a dense silicon oxide layer, resulting in the low temperature oxidation behavior of amorphous silicon nanoparticles. These results provide insight into kinetics and chemistry of amorphous silicon oxidation in the thin film regime.