A Raman Spectroscopy Study of Individual SiC Nanowires

Abstract

Raman spectroscopy of a single 40 nm 3C‐SiC nanowire (NW) has been achieved at room temperature with the use of surface‐enhanced Raman scattering (SERS). The structure used to enhance the Raman scattering process is based on a tungsten tip covered by a thin gold layer; a NW is attached to the apex of this tip. The specific dimensions of the SiC NWs (diameters are a few tens of nanometers and lengths are a few micrometers) allow us to study several parts of an individual NW according to the lateral resolution of the Raman microspectrometer. High‐resolution transmission electron microscopy (HRTEM) images show both atomic arrangements in the SiC NWs with growth predominantly in the [111] direction and abundant structural defects. Effort has been focused on the correlation between the Raman spectroscopic profiles and the structural deformations. The Fano interference features of the sharp phonon lines have been used to evaluate the free carrier concentration.

Conversion of wooden structures into porous SiC with shape memory synthesis

“…Due to this large FWHM we cannot determine the exact peak position of each sample and cannot claim the exact polymorph type with certainty, but simple association, in the table, makes some suggestions obvious. In Table 4, we can see that there are differences in the positions of the peaks and from the comparison with literature [43,44] it is suggested that these can be from 2H or 4H-SiC. These assignments are also supported by comparison with the XRD results for the amounts of different polymorphs in the samples as shown in Table 3.…”

“…Raman spectroscopy is one of the most sensitive techniques for distinguishing between the different polymorphic types of SiC [43,44]. Silicon carbide is known to have a large number of polymorphs, of which b-SiC has a zinc blende kind of structure with the smallest unit cell of all the SiC polymorphs.…”

“…Silicon carbide is known to have a large number of polymorphs, of which b-SiC has a zinc blende kind of structure with the smallest unit cell of all the SiC polymorphs. Bulk bSiC has two optical modes at the G point of the Brillouin zone, a transverse optic (TO) mode at 796 cm À1 and a longitudinal optic (LO) mode at 972 cm À1 [44]. These modes have different energies, which in ''higher'' polytypes can be used to distinguish the different polymorphs.…”

SiC nanowires: material and devices

“…Figures 9a to 9d show HRTEM images of SiC nanowires with crystal defects mainly SFs. The spatial extension of the defected zone can be small as in the case of figure 9d [32] or NW-diameterlarge ( figure 9a and b) [49] or even extending in the whole NW (figure 9c) [46]. In most cases the SFs are perpendicular to the nanowire axis (Figure 9a, b and c).…”

“…In the case of SiC NWs, many different Raman studies have been reported [32,46,49,53,54]. A typical example is shown in figure 11 (after [46]).…”