Blue Light Emission from Rapid-Thermal-Oxidized Porous Silicon

We have converted the hydrogen-passivated surface of porous Si prepared by electrochemical etching into a stable oxidized one using a rapid thermal oxidation process. At a high oxidation temperature (T ox) above about 800° C, blue photoluminescence (PL) with a peak wavelength of about 400 nm was clearly observed. On the other hand, at low T ox below about 800° C, the PL peak remained at about 750 nm, which is similar to that of as-anodized porous Si. From Fourier transform infrared (ETIR) spectra, we found that the PL spectra are closely related to the structure of the oxygen-terminated surface on Si nanocrystallites. Spectroscopic data suggest that the red PL and the blue PL originate from a surface state and a quantum-confinement state, respectively.