Study of the permeability of thin films of a-Si:H using MeV ion beams

MeV heavy ion irradiation of hydrogenated plasma-deposited silicon nitride induces formation of the volatile molecules H-2 and N-2 inside the material. This type of nitride appears permeable for these molecules and they effuse at relatively low temperature. These effusing molecules are used to study the low temperature permeation in a 100 nm hydrogenated amorphous silicon layer, deposited onto the nitride. Upon irradiation of the double layer stack with 43.3 MeV Ag ions, appearance of D-2 and N-2 from the bottom deuterated silicon nitride layer in the vacuum does not take place up to an ion fluence of 3 x 10(12) ions/cm(2). This shows that the 100 nm plasma-deposited hydrogenated amorphous silicon top layer is initially not permeable for D-2 and N-2 molecules. (C) 2002 Elsevier Science B.V. All rights reserved.