Positron lifetime and microstructural characterisation of a-Si:H deposited by low temperature HW-CVD on paper substrates

In thin film electronic applications, the limiting factor, in terms of cost and usability, is generally the substrate material. As a consequence, different materials are being investigated as potential lightweight, inexpensive and flexible substrates. In this respect, we have been the first research collaboration to produce silicon-based electronics on paper substrates. Here we present structural characterisation of hydrogenated amorphous silicon (a-Si:H) layers deposited on 80 g m⁻² wood-free paper, with and without an intermediate metallic interlayer, using low temperature hot wire chemical vapour deposition (HW-CVD). Both pulsed positron beam profiling and X-ray diffraction studies indicate that the growth rate on the uncoated substrate is slightly higher than with prior metallization. There is no evidence of a crystalline phase or voids in the a-Si:H layers. The internal defect structure is similar, with a dominant dangling bond complex of similar size, which has a slightly longer lifetime than in layers grown at higher temperatures on conventional substrates.