Three chemical vapor deposited diamond films were studied by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Enhanced 13C direct-polarization spectra of diamond films were obtained by irradiating the samples with microwaves at or near electron spin resonance Larmor frequency of carbon center free radicals. No NMR signal for sp2 hybridized carbons could be observed. From the curve of the DNP enhancement as a function of frequency, it is found that the dominant DNP mechanism is the solid-state effect. The 13C cross-polarization spectrum, which is an evidence for existence of the proton defect in the lattice of diamond films, is much broader than the 13C single pulse spectrum. The reason is discussed shortly.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics