Laser-induced reversible and irreversible changes in silicon nanostructures : One- and multi-phonon Raman scattering study

Reversible/irreversible changes in the Raman spectra of mesoporous silicon (meso-PSi) induced by laser heating were investigated. It is shown that whereas identical Raman spectra of single crystalline silicon can be obtained at different laser irradiances, these spectra change significantly in both reversible and irreversible ways in silicon nanostructures such as porous silicon (PSi). Whereas band shift and broadening in first- and second-order scattering were found to be reversible, surface phonon scattering events changed irreversibly. Given the importance of Raman spectroscopy in characterizing the pivotal role played by surface chemical bonds such as Si-H in the performance of PSi-based photovoltaics and microelectronics, our study highlights that great care must be taken to avoid Raman laser-induced effects on these bonds. © 2011 American Chemical Society.