Raman study of the relationship between nanoparticles and photoluminescence in spark-processed silicon

Abstract

Spark-processed silicon (sp-Si) that strongly photoluminesces (PL) in the blue and green regions of the visible spectrum has been analyzed by Raman scattering, in order to probe a possible relationship between the presence and size of Si nanoparticles and PL emission wavelengths. Spatially resolved Raman spectra were measured across spark-processed regions, scanning areas which vary in PL intensity but not wavelength. The observed small shifts and broadenings of the Raman signals indicate the presence of Si particles having diameters of about 15 nm in the central, photoluminescing section of the sp region. Slightly smaller Si crystallites with sizes of about 8–9 nm were found in the halo region which does not contribute to PL. Furthermore, the Raman peak shifts and broadenings are essentially identical for blue and green photoluminescing sp-Si. These results suggest that the PL of sp-Si is not caused by a quantum-size effect which is coupled to the presence of Si nanoparticles.