Deuterium effusion from nanocrystalline boron nitride thin films

Abstract

Deuterium thermal desorption experiments were performed on hexagonal(h-BN)and cubic (c-BN) boron nitride thin films deposited on (100) oriented Sisubstrate by radio frequency (rf) magnetron sputtering. BN samples weredeuterated by thermal annealing at 673 K in a 10-4 mbar D2atmosphere for 100 min. No differences were observed between c-BN and h-BNthin film samples in the effusion process, which occurred through a thermalactivated heterogeneous first order kinetics. The activation energy fordesorption exhibited a Gaussian distribution peaked at 2.28±0.01 eVwith 0.18±0.02 eV semidispersion. This result indicated the breakingof the N-D and B-D chemical bonds, probably located at the grainboundaries of the nanocrystalline material, as the rate limiting step inthe effusion kinetics. When the deuteration of the BN thin film samplesoccurred by 20 keV D2 ion implantation, deuterium effusion is controlledby the migration of deuterium atoms to the sample surface through grainboundaries path and is characterized by 0.52±0.03 eV activationenergy.