Phonon Confinement in SiC Nanocrystals: Comparison of the Size Determination Using Transmission Electron Microscopy and Raman Spectroscopy

Abstract

Silicon carbide fibers of different generation/processing routes (NLM-Nicalon and Tyranno SA3) were thermally treated to trigger the growth of nanocrystals, which were analyzed using Raman spectroscopy and transmission electron microscopy (TEM). The nanocrystals were also aged in molten sodium nitrate to investigate their reactivity. The spatial correlation model has been used to model the Raman spectra and extract accurate and statistical information on the nanocrystallites' structure and dimension. For the NLM fibers, an average size of 2.5 to 7.0 nm was calculated, which was in good agreement with TEM observations. For the Tyranno SA3 fiber, despite the heavily faulted stacking sequence, the Raman peaks remained sharp, indicating that the crystallite dimension calculated from the Raman spectra is only dependent on the actual size of the nanocrystals and is not affected by the sequence of the stacking faults.

Quantum‐chemical perspective of nanoscale Raman spectroscopy with the three‐dimensional phonon confinement model

“…However, stacking faults are observed in a significant amount of nanoparticles [22] . Interestingly, the combined TEM+Raman studies have shown that the non-periodic arrangement of the stacking faults does not affect the phonon confinement length in SiC [23] . Therefore, it is likely that for the case of NDs the defects give minor contribution to the phonon coherence length, and the correct interpretation of the "Raman size" is the diameter of the diamond core.…”

Raman investigation of defective SiC nanocrystals

“…However, because crystalline perfection is destroyed, the phonon function of polycrystals is spatially confined, which results in an exploration of the wavevectors space and subsequent peak shifts and band broadening. [14,20] At the same time, forbidden modes in perfect crystal may appear like the observed modes at about 770 and 840 cm À1 in Fig. 2 [21] is shown in Fig.…”

“…[11] This model has been proved proper in characterizing nano particle, nano rod, and porous material. [10][11][12][13][14][15][16][17] Although RWL model is a powerful tool to analyze the relationship between microstructure and Raman lineshape, choosing proper parameters for calculation is always a challenge. Improper parameter setting would decrease accuracy of RWL model calculation.…”

SiC, from Amorphous to Nanosized Materials, the Exemple of SiC Fibres Issued of Polymer Precursors

“…Silicon Carbide -Materials, Processing and Applications in Electronic Devices 166 surrounded by highly disorderd/amorphous SiC interphase and free carbon grains (Monthioux et al, 1990;idem, 1991;Havel, 2004;Havel et al, 2007).…”

“…(Table 1). Structural studies of SiC nanocrystals were carried out on fragments of fibres deposited on a copper grid after crushing in an agate mortar (Havel, 2004;Havel et al, 2007). In SA3 TM fibre the carbon phase appears to be well organized, graphitic, according to the narrow doublet of the Raman spectra (Fig.…”