Red to green rainbow photoluminescence from unoxidized silicon nanocrystallites

We prepared luminescent silicon by incorporating H2O2 in the anodizing process. Under UV excitation, our samples appear reddish, orangish, yellowish to greenish as the electrolyte-air interface at the meniscus is approached. Under high current anodization, the emission becomes broad but unstable. The time characteristics of all the emission regions are in the range of 1–10 μs. The results are consistent with a significant reduction of crystallite sizes, and may be explained via novel Si–Si dimer surface states that are induced by quantum confinement.