Micro­Raman Scattering of Nanoscale Silicon in Amorphous and Porous Silicon

Thesize effect of nanoscale silicon in both amorphous and porous silicon was investigated with micro­Raman spectroscopy. Silicon nanostructers in amorphous silicon were deposited on quartz substrates by plasma enhanced chemical vapor deposition (PECVD) with deposition powers of 15, 30 and 50W. Micro­Raman spectra of the nanostructured silicon show the T 2g Raman active mode shifting from the 521 cm ­1 crystalline Si Raman line to 494, 499 and 504 cm ­1 as deposition power increased. Large Raman mode shifts, up to 27 cm ­1 and broadening up to 23 cm ­1 of the T 2g Raman­active mode is attributed to a phonon confinement effect which {did what with power}. The analysis of micro­Raman scattering data is useful to understand the role of deposition condition of the silicon sample. In addition, enhanced micro­Raman scattering intensity of porous silicon prepared using double cell electrochemical etching through various current densities such as 10, 50 and 125 mA/cm 2 has also been investigated. The effect of phonon confinement on the nanoscale porous silicon has been quantified. The relationship between Raman shift and stress on the porous silicon has been evaluated.