Deuterium effusion from nanocrystalline boron nitride thin films

Deuterium thermal desorption experiments were performed on hexagonal (h-BN) and cubic (c-BN) boron nitride thin films deposited on (100) oriented Si s ubstrate by radio frequency (rf) magnetron sputtering. BN samples were deut erated by thermal annealing at 673 K in a 10(-4) mbar D-2 atmosphere for 10 0 min. No differences were observed between c-BN and h-BN thin film samples in the effusion process, which occurred through a thermal activated hetero geneous first order kinetics. The activation energy for desorption exhibite d a Gaussian distribution peaked at 2.28 +/- 0.01 eV with 0.18 +/- 0.02 eV semidispersion. This result indicated the breaking of the N-D and B-D chemi cal bonds, probably located at the grain boundaries of the nanocrystalline material, as the rate limiting step in the effusion kinetics. When the deut eration of the BN thin film samples occurred by 20 keV D-2 ion implantation , deuterium effusion is controlled by the migration of deuterium atoms to t he sample surface through grain boundaries path and is characterized by 0.5 2 +/- 0.03 eV activation energy.