Room-temperature atmospheric oxidation of Si nanocrystals after HF etching

The effect of HF etching of the silicon oxide shell covering the surface of Si nanocrystals (NCs) on the subsequent room-temperature atmospheric oxidation of Si-NCs has been investigated by means of photoluminescence measurements, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy. After the HF etching, the surface of Si-NCs is found to be H terminated. The HF etching also restructures the surface of Si-NCs. This leads to a decrease in the incorporation of O during subsequent oxidation, which finally results in silicon suboxide SiO_1.9. In contrast, without the HF etching stoichiometric SiO₂ is formed. A smaller ratio of O to Si in the silicon oxide results in a higher density of defects. This contributes to a more significant oxidation-induced decrease in the intensity of photoluminescence from Si-NCs after the HF etching than without the HF etching.