EPR and optical studies on as grown polycrystalline diamond and diamond films annealed between 1100 and 1900 K

Abstract

We report a systematic study by electron paramagnetic resonance (EPR), and infrared absorption of as grown and annealed free standing polycrystalline diamond films. In all CVD diamond films studied an EPR resonance is observed at g=2.0028(2). Comparison of the local and bulk concentrations indicated that these centres are inhomogeneously distributed in the films, where as the single substitutional nitrogen centres appear homogeneously distributed throughout the CVD diamond. The strength of the total EPR absorption at g=2.0028 correlates with the total infrared absorption in the CH region. Upon annealing to 1900 K in vacuum the intensity of the resonance at g=2.0028 decreases significantly in intensity and narrows slightly. During this treatment the sharp infrared absorption line at 2820 cm(-1) increased and then decreased in intensity, but besides this there were no significant changes in the infrared absorption The results suggest that the dangling bonds responsible for the g=2.0028 EPR absorption are not located in the diamond lattice but are to be found on grain boundaries or in non-diamond intergranular material and are compensated during annealing when hydrogen on the grain boundaries, or in intergranular material becomes mobile. New unidentified EPR centres are produced when the samples are annealed in vacuum above 1800 K