Study on the applied limitation of the micro-crystal model for Raman spectra of nano-crystalline semiconductors

The limitation in sample size and the choice in parameters for the application of the micro‐crystal (MC) model have been tested and discussed. The testing was performed through the fitting of calculated Raman spectra by using the MC model with the observed Raman spectra for nearly uniform‐sized nano‐crystalline (NC)‐Si of smaller than 2 nm. The results showed that the good fittings could not be obtained, if the phonon dispersion curves ω(q) and Raman linewidths Γ of bulk‐crystals (BCs) were used, i.e. if the bulk‐like approximation (BLA) was used in the fitting. Moreover, an analysis of the fitting results indicates that when the size of NC‐Si is smaller than about 4 nm, the MC model based on –BLA will be invalid. Copyright © 2008 John Wiley & Sons, Ltd.