Concerning the $506cm−1$ band in the Raman spectrum of silicon nanowires

Silicon nanowires synthesized on an amorphous substrate by the vapor-liquid-solid method were studied using Raman spectroscopy and ab initio calculations. The authors show that the Raman spectrum of Si nanowires is compatible with the existence of two distinct phases. The Raman spectra revealed a peak centered around $517cm−1$ as expected for the nanosized diamond cubic phase (Si-I). However, two new contributions, centered around 506 and $516cm−1$⁠, arose which they attributed to the diamond hexagonal phase (Si-IV). The identification of these Raman peaks clarifies the controversy surrounding the vibration modes of Si-IV previously reported in the literature.