Raman scattering studies of chemical-vapor-deposited cubic SiC films of (100) Si

Abstract

Raman backscattering studies for a series of cubic SiC (3C-SiC) single-crystal films grown on (100)Si by way of chemical vapor deposition (CVD) with SiC film thicknesses dSiC from 600 Å to 17 μm are performed. Raman spectra of samples with dSiC>4 μm show a sharp and strong feature which obeys the selection rule for the 3C-SiC LO(Γ) phonon line. The Raman signals from the SiC film and the Si substrate show the same polarization behavior which confirms that the crystalline orientations of the Si substrate and 3C-SiC film are the same. Although there is a big lattice mismatch of 20% between 3C-SiC and Si the observed Raman shifts between 3C-SiC/Si and free 3C-SiC films are ≤2 cm−1 and reflect strains of 0.1%–0.2% in films thicker than 4 μm. Some interesting enhancements of Si and 3C-SiC Raman signals are reported. The Si 522 cm−1 phonon from a Si wafer is enhanced in intensity by a factor of 2–3 due to a CVD overlayer of cubic SiC. Furthermore, the 3C-SiC longitudinal optical phonon at the Γ point, LO(Γ), from SiC/Si samples is enhanced by a factor of 2 or 3 following the removal of the Si substrate. The strict selection rules are no longer obeyed in this case. The former is possibly due to the electric-field-induced inelastic scattering from the SiC/Si heterojunction. The latter is explained by the multiple reflection in free 3C-SiC films. Our theoretical analysis shows that if the cross section for forward scattering is about one order of magnitude larger than that for backscattering, this enhancement will appear. The forward scattering has different selection rules from the back scattering and thus could lead to the appearance of the forbidden transverse optical phonon and the depolarization of the 3C-SiC Raman phonons from the SiC free films. The variation of the Raman spectrum with incident power has also been studied. The Raman cross section for 3C-SiC is estimated by a new method. The wavelength shifts of 3C-SiC LO(Γ) phonons taken from SiC/Si or free films are measured and explained.

Synthesis of Inorganic–Organic Diblock Copolymers as a Precursor of Ordered Mesoporous SiCN Ceramic

“…On the other hand, the preparation of mesoporous silicon carbide with a unique stability and strength using hard templates has attracted considerable interest. [4][5][6][7][8] However, hard-template routes are not suitable for the industrial production of powder materials due to engineering difficulties, and require a harmful etching step, most commonly with strong acid, which limits the coating processiblity to substrates. Therefore, soft-template routes using surfactants and block copolymers have attracted substantial attention for the creation of well-ordered nanostructured materials with facile applications on a large scale.…”

Analysis of grain boundary sinks and interstitial diffusion in neutron-irradiated SiC

“…The material is typically free of micro cracks or other large flaws, but atomic layer stacking faults on the {111} planes are common. There is no porosity in this CVD SiC, and the material has essentially theoretical density (approximately 3.21 g/cm 3 ). Results of the quantitative analysis on the DZ width and defect microstructures examined in the regions well away from the DZ are summarized in Table I.…”

“…Silicon carbide (SiC) in various forms is considered a promising structural material for nuclear, 1, 2 electronic and optoelectronic devices applications, 3 because of its high thermal stability, excellent resistance to chemical attack, high thermal conductivity, and high electron saturation drift velocity. While in use or production, SiC is subjected to neutronirradiation or ion-irradiation of dopants which can produce the Frenkel pairs both in the silicon and carbon sublattices in addition to a clustered defects and antisite defects.…”

Silver assisted crack healing in SiC

“…Before heat treatment, the Raman spectrum of the un-indented surface ( Fig. 2(a), curve I) shows two strong characteristic peaks centered at 796 and 972 cm À1 , which are attributed to the first order of transverse optical (TO) and longitudinal optical (LO) phonons of b-SiC [22,23]. Two additional weak peaks centered at 1524 and 1713 cm À1 represent the second-order Raman scattering of b-…”