After oxidation promoted by gamma‐ray irradiation, in the photoluminescence (PL) spectra of Sm doped porous silicon (PS), there are three sharp peaks, superimposed on a broad band, with wavelengths near to those of the Sm doped SiO2 [R. Morimo, T. Mizushima, and H. Okumura, J. Electrochem. Soc. 137, 2340 (1990)]. The experimental results indicate that Sm‐related luminescence centers can be created within the oxide of porous silicon, and only in porous silicon with high porosity can the Sm‐related luminescence be found in the SiO2 layer. This experimental result can be explained by the fact that the excitation of electron‐hole pairs occurs in nanoscale silicon, and the recombination occurs at the Sm‐related luminescence centers in SiO2 layers covering nanoscale silicon.