Thermal D-desorption experiments were performed on thin films of hexagonal and cubic material which had been deposited onto (100)-oriented Si substrates by radio-frequency magnetron sputtering. Samples were deuterated by annealing (673K, 100min) in a 10-4 mbar D atmosphere. No differences were observed between cubic and hexagonal thin-film samples during effusion; which occurred via thermally activated heterogeneous first-order kinetics. The activation energy for desorption exhibited a Gaussian distribution that peaked at 2.28eV, with a 0.18eV semi-dispersion. This result reflected the breaking of the N-D and B-D chemical bonds (probably located at the grain boundaries of the nanocrystalline material) as being the rate-limiting step of the effusion kinetics. When deuteration of the thin-film samples involved 20keV D2-ion implantation, D effusion was controlled by the migration of D atoms to the sample surface through grain boundary paths, and was characterized by an activation energy of 0.52eV.

Deuterium Effusion from Nanocrystalline Boron Nitride Thin Films. Checchetto, A.Miotello, R.S.Brusa: Journal of Physics - Condensed Matter, 2001, 13[26], 5853-64