Amorphousness-like nature of nano-crystalline polar semiconductors

Raman spectroscopy has been used in the identification of crystallography property of nano-semiconductors. The identified result by Raman spectroscopy is consistent with that by the X-ray refraction (XRD) in bulk materials and in non-polar semiconductors, e.g., porous silicon and Si nano-wires. But for nano-polar semiconductor SiC, GaN and ZnO, their Raman spectra can not described by the crystalline model but the amorphous model related to the phonon density of states (PDOS). Moreover, it is found for these samples that Raman frequencies excided by different incident wavelengths were not changed, matching the no change characteristic of PODS with sample sizes. Therefore above results may indicate that these nano-polar semiconductors possess of amorphousness-like nature although they are crystalline by XRD measurements. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.