Micro-Raman Scattering of Nanoscale Silicon in Amorphous and Porous Silicon

Abstract

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.

The optical performance of random and periodic textured mono crystalline silicon surfaces for photovoltaic applications

“…Similar Raman shifts are observed in nano-c-Si and micro-c-Si, where crystalline grains are embedded in an amorphous Si phase [22]. In these materials the exact shift was demonstrated to be a function of the crystalline grain size [20]. The increase of the 500 cm À1 peak in reference to the 520 cm À1 peak, with increasing d imp , indicates an increase of the fraction of strained c-Si in reference to the mono-c-Si phase.…”

“…The latter peak corresponds the vibration of bulk mono-c-Si material. The peak at 500 cm À1 is associated to a poly-crystalline phase [20,21], with the Raman shift in reference to mono-c-Si resulting from strain from the crystalline grains. Similar Raman shifts are observed in nano-c-Si and micro-c-Si, where crystalline grains are embedded in an amorphous Si phase [22].…”