HYDROGEN-RELATED DEFECTS IN POLYCRYSTALLINE CVD DIAMOND

By simulating the line shapes of a commonly observed S=1/2 electron pa ramagnetic resonance (EPR) center in polycrystalline chemical vapor de posited (CVD) diamond at 9.8, 14, 20, and 35 GHz, we conclude that the EPR signal, which we label H1, results from a unique defect with a si ngle hydrogen atom similar to 1.9 Angstrom away from the unpaired elec tronic spin. We report also 14 and 20 GHz studies of an additional hyd rogen-related EPR center, labeled H2, which is similar; however, the h ydrogen is similar to 2.3 Angstrom away. We propose that, in each case , a hydrogen atom has entered a stretched bond at a grain boundary or other extended misfit region in the CVD material, allowing the carbons to relax backward, one bonding to the hydrogen, the other with an unp aired electron in its dangling bond. These results may provide importa nt insight into the recently discovered phenomenon of hydrogen activat ion at grain boundaries in silicon.