Characterization of polycrystalline diamond by electron spin resonance and related techniques

CVD diamond films with nitrogen content varying from 10 ppm to 132 ppm have been studied by electrons spin resonance (ESR), light-induced ESR (LESR) as well as electrically detected magnetic resonance (EDMR). Two characteristic signals have been observed. A carbon-related line with g = 2.0029 ± 0.0002 and width 4 ± 1 G, is observed in ESR, LESR and EDMR. The intensity of this line measured by ESR increases linearly with nitrogen content. For low- defect-density samples, or after illuminating the high-defect density samples with UV light, a second signal is observed both in ESR and LESR, but not in EDMR, with a central line at g = 2.0024 ± 0.0001 and width 0.2 ± 0.1 G and related hyperfine satellites approx. 30 G away from the central line. This line is assigned to isolated substitutional nitrogen. The density of N-related paramagnetic states is strongly affected by illumination and heat treatments, while the line-shape is found to be affected by crystallite disorientation. The mechanism of nitrogen incorporation, and the consequences on the band gap density of states are discussed. EDMR measurements indicate that the dark conductivity at room temperature in CVD-diamond is dominated by hopping at the g = 2.0029 defect. PACS: 68.55.Jk, 81.05.Tp, 85.40.Ry, 76.30.Da.