H-1-NMR STUDIES ON THE EFFECTS OF ANNEALING ON CHEMICAL-VAPOR-DEPOSITED (CVD) DIAMOND

A proton nuclear magnetic resonance (H-1 NMR) spectrum of diamond produced by chemical vapor deposition typically exhibits both a narrow lorentzian and a broad gaussian line. The spin-lattice relaxation time constants of the two components are different in one sample and vary from sample to sample. Typical values are in the range of approximately 50 ms to l s. There is little or no hydrogen evolution on annealing in a nitrogen atmosphere at temperatures less than 750-degrees-C. However, T1 increases on annealing and the line shape changes as the contribution due to the narrow component decreases. The magnetization recovers as M = M0[1 - exp(- t/T1)n], where 0.5 less-than-or-equal-to n less-than-or-equal-to 1. The values of n and T1 increase with annealing indicating a change in the number of relaxation centers present in the sample.