MICROSTRUCTURE OF POROUS SILICON AND ITS CORRELATION WITH PHOTOLUMINESCENCE

Microstructure of porous silicon (PS) was observed through high-resolu tion transmission electron microscope to study a relationship between the microstructure and a photoluminescence (PL) from PS. Three PS samp les were made through anodization with different current densities. Th e samples had different PL spectra and were supposed to have different microstructures. Threadlike structures of Si and Si crystallites in t he PS layer were observed in all the samples. The threadlike structure has the same density in all samples and has very little structural ch ange, in spite of a significant change of PL spectra. The density of t he Si crystallites varies for the samples and has a strong correlation with the PL intensity. No particular change of crystallites shape was observed. The size of the crystallites ranges from a few nanometers t o a few tens of nanometers. Although no positive evidence to a quantum confinement is indicated, the Si crystallites are responsible for a l ight emission from PS.