[Excitation-wavelength dependent photoluminescence from porous silicon]

With the technique of fluorescence spectral analysis, the dependence of the fluorescence from porous silicon on the excitation wavelength was investigated. It was found when the excitation wavelength decreases from 650 to 340 nm, the fluorescence spectrum of porous silicon blue shifts continuously from 780 to 490 nm. Using scanning electron microscopy (SEM) and computer simulation, the cross-sectional structures of porous silicon were studied. The authors' results showed that the microstructures of porous silicon exhibit fractal characteristics. With the additional information extracted from the excitation spectra of porous silicon, the authors' results can be interpreted in terms of the quantum size effect and the fractal structures of porous silicon.