Spins and microstructure of hydrogenated amorphous carbon : A multiple frequency electron paramagnetic resonance study

• Polymer-like and diamond-like hydrogenated amorphous carbon films, characterized by high spin concentrations of 1020 cm-3, have been studied by multiple frequency electron paramagnetic resonance (EPR) spectroscopy at 9, 35, and 94 GHz. Whereas the low-frequency measurements show only one single symmetric EPR line, the high-frequency measurements reveal the anisotropic nature of the g tensor. They show the presence of two different paramagnetic centers with anisotropic g tensors of g?(1) = 2.005, g?(1) ˜ 2.003, and g?(2) = 2.010, g?(2) ˜ 2.003. We attribute both to localized p states on nanosized sp2 graphitic clusters. The g? values of the g tensors, which are correlated to the size of the graphite like carbon clusters, indicate two different cluster sizes with values below 50 Å. © 2001 American Institute of Physics.

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