Hydrogen diffusion and stability in polycrystalline CVD undoped diamond

Diffusion profiles and effusion experiments performed on post-hydrogenated (deuterated) CVD diamond layers (grain size 2 and 0.2 mum) are reported in order to study the configurations and stability of hydrogen bonding in poly crystalline undoped CVD diamond. Deuterium is used as a tracer to improve t he hydrogen detection limit. The diamond layers are first annealed at 1200 degreesC in order to out-diffuse hydrogen present in the as-grown sample. T hen the samples are exposed either to a radiofrequency plasma or a microwav e plasma and the deuterium diffusion profiles are analyzed by secondary ion mass spectrometry. For r.f. and microwave plasma, the diffusion profiles a re explained in term of trapping on plasma-induced defects near the surface and/or on inter- and intra-granular defects. The mean free paths of deuter ium and capture radius of traps are calculated by fitting the deuterium dif fusion profiles and depend on the grain sizes. Some CVD diamond layers are deposited using a gas mixture (CH4 + D-2) and a deuterium concentration of 3 x 10(19) cm(-1), originating from the vector gas, is found in these as-gr own samples. The stabilities of deuterium bonding in as-grown and post-deut erated samples are compared. (C) 2001 Elsevier Science B.V. All rights rese rved.