The great potential of the silicon carbide (SiC) and diamond nanoparticles
for future applications in spintronics initiates detailed investigation of the effects of
impurities and defects in their electronic characteristics. Among impurities, nitrogen
doped SiC nanoparticles are an important item to be studied, because nitrogen donors
are common contaminations of an n-type SiC bulk material. The first information about
the shallow donor state of nitrogen in SiC nanoparticles and influence of the hydrogen
as well as intrinsic defects on electronic properties of nitrogen was presented in this
chapter. The delocalization of the nitrogen wave function was observed with the
reduction in the nanoparticle size with the onset of about d < 50 nm. The delocalization
of the nitrogen wave function gives rise to the overlap between wavefunctions of the
neighboring donors and transformation of the nitrogen triplet line into one single
exchange EPR line. The size-dependent effect was also observed for paramagnetic
substitutional nitrogen defects (P1) in nanodiamonds representing free electron
interacting with the 14N nuclear spin (I = 1). The decrease of size of nanoparticle down
to d < 80 nm led to a transformation of the hyperfine structure of the P1 defect into a
one EPR line caused by dipole-dipole and/or exchange couplings of P1 spins with the
rising amount of surface spins, which becomes more effective in nano-sized particles.
Keywords: Carbon vacancy, Compensation, Delocalization, Dipole-dipole
interaction, Donor wavefunction, EPR, ENDOR, Exchange interaction, ED EPR,
Hydrogen, Hydrogen retention, Hyperfine interaction, Intrinsic defects,
Nanodiamonds, Nanoparticles, Nitrogen, Silicon carbide, Size-dependent effect,
Superhyperfine interaction, Surface defects.
