Low-hydrogen-concentration a-Si:H grown by HW-CVD forms a continuous random network with no detectable free volume in the form of microvoids, and no evidence of a microcrystalline phase. Over a wide temperature range we observe a single positron state in the amorphous network with a temperature-independent lifetime of 322 ps. From the temperature dependence of the positron diffusion we show that this is a localized state and present direct observation of hopping diffusion of positrons. On annealing up to 400 °C the amorphous network is seen to relax and the first stages of crystallization occur. There is also evidence of vacancy clustering to form a low concentration of microvoids. The structural relaxation has a very low-activation energy, around 0.1 eV, and is interpreted in terms of a reconfiguration of the fundamental defect identifed by positron annihilation.
|Number of pages||5|
|Journal||Journal of Non-Crystalline Solids|
|Issue number||PART 1|
|Publication status||Published - Apr 2002|
ASJC Scopus subject areas
- Ceramics and Composites
- Electronic, Optical and Magnetic Materials