Morphological and crystallographic defect properties of microcrystalline silicon: a comparison between different growth modes

The microstructure of thin microcrystalline silicon films deposited by plasma-enhanced chemical vapour deposition has been studied by transmission electron microscopy. A comparison between continuous growth, layer-by-layer growth and epitaxial growth shows that the process history is not reflected in the structure of the films: (1) For continuous deposition and layer-by-layer deposition on silicon dioxide, defect-rich nuclei grow to twinned columns. The layer-by-layer technique was found not to be beneficial to the bulk structure in that nucleation density and grain sizes are comparable for both techniques. (2) Epitaxial growth occurs under the same plasma conditions on ex-situ wet etched silicon (100) surfaces, but is limited in thickness and followed by microcrystalline growth. The structural similarity points to a common dominant growth mechanism for continuous and layer-by-layer deposition, which may be affected by mechanisms that also lead to limited epitaxial thickness in molecular-beam epitaxy. (C) 1998 Elsevier Science B.V. All rights reserved.