Chemical vapour deposited polycrystalline layers were deposited by using a gas mixture (CH4+D2), and a D concentration of 3 x 1019/cm3 (originating from the vector gas) was found in the as-grown samples. Samples were first annealed at 1200C, exposed to a D microwave or radio-frequency plasma, and the D diffusion profiles analyzed. The profiles were explained in term of trapping on Chemical vapour deposited polycrystalline layers were deposited by using a gas mixture (CH4+D2), and a D concentration of 3 x 1019/cm3 (originating from the vector gas) was found in the as-grown samples. Samples were first annealed at 1200C, exposed to a D microwave or radio-frequency plasma, and the D diffusion profiles analyzed. The profiles were explained in term of trapping on