INFLUENCE OF HYDROGEN ON THE STRUCTURAL ORDER OF MICROCRYSTALLINE SILICON DURING THE GROWTH-PROCESS

Commonly, the transition of amorphous to microcrystalline growth is ac hieved by diluting silane (SiH4,) with hydrogen (H-2). Increasing hydr ogen dilution causes an increase of crystallinity. However, at high H dilution (Delta(H) > 0.98), the crystallinity is found to decrease aft er reaching a maximum. A decrease of crystallinity is also observed in microcrystalline silicon (mu c-Si) samples after a post-hydrogenation treatment. These experiments show that hydrogen incorporation into th e structure leads to loss in the structural order due to an H-induced conversion of Si-Si bonds into strained or weak Si-Si bonds. The impli cations of these results for the growth mechanisms are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.