Raman spectral study of silicon nanowires

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Abstract
Raman spectra of silicon nanowires (Si NW’s) have been analyzed, and the observed Raman peaks were assigned. The typical features of the first-order Raman peaks of the optical phonons were found matching those predicted by the quantum confinement effect. However, the sizes of Si NW’s, derived from the microcrystal model (MCM) of Raman spectra do not fit the usual confined size, the diameter, of the nanowires from transmission electron microscope images. Abundant structure defects can be observed in Si NW’s so that the Si NW’s actually consist of many smaller Si grains. The size of such Si grains was found to give a better agreement with the size derived from the Raman spectra. This indicates that MCM can be used to interpret the Raman spectrum of Si NW’s as long as one takes into account the influence of defect on the confined size.