In this chapter, we present the study of SiC nanoparticles obtained by
pyrolysis and self-propagating high temperature synthesis (SHS) method using multiapproaches
electron paramagnetic resonance (EPR) methods, including continuous
wave EPR, field swept electron spin echo (FS ESE), pulsed electron nuclear double
resonance (ENDOR) and four-pulse electron spin echo envelope modulation ESEEM
(hyperfine sublevel correlation, HYSCORE) spectroscopy. Three paramagnetic defects
were observed in SiC nanoparticles. Two of them with giso = 2.0029(3) and giso =
2.0043(3) were assigned to carbon vacancy VC localized in the cubic (β) and hexagonal
(α) phase of the SiC nanoparticles, respectively. The paramagnetic defect with giso =
2.0031(3) was attributed to the sp3-coordinated carbon dangling bonds (CDB) located
in the carbon excess phase of the SiC nanoparticles. The paramagnetic defect with giso=
2.0037(3), which was observed only in SiC nanoparticles obtained by SHS method was
attributed to the bulk intrinsic defect having a Si-NSi2 configuration and located in
α-Si3N4 phase of the SiC nanoparticles. A high delocalization of the electronic
wavefunction of the unpaired electron for the carbon vacancy VC localized in the cubic
crystalline phase of the SiC nanoparticles was found from the detail study of the VC
ligand structure by pulse ENDOR and HYSCORE methods.
Keywords: a-Si3N4 phase, Carbon dangling bonds, Carbon excess, Carbonvacancy, Davies ENDOR, EPR, Field-swept electron spin echo (FS ESE), Hydrogen, Hyperfine coupling, HYSCORE, Intrinsic defects, Mims ENDOR, Nanoparticles, Pulse EPR, Silicon carbide (SiC), Superhyperfine coupling, Spin density, Stoichiometry, α-SiC phase, β-SiC phase.
