Hydrogen induced promotion of nanocrystallization from He-diluted SiH4 plasma

The effect of partial hydrogen dilution on the mostly helium diluted silane plasma in controlling the nanocrystallization process in the Si : H network was studied systematically. The parametric conditions were chosen in such a way as to produce the basic matrix as a mixed phase heterogeneous material in the neighbourhood of the amorphous to nanocrystalline transition zone, but dominated by the amorphous component, which could easily trigger nanocrystallization on favourable parametric changes. The relative influence of He and H-2 was closely monitored, by virtue of their individual presence in the plasma in different proportions, in the nanocrystallization process that might occur within the Si : H network. Controlled hydrogenation to such a heterogeneous structure, during growth, has been identified as the favoured route for attaining spontaneous nanocrystallization in the network. The beneficial aspects of He-dilution in enhancing the growth rate and initiating nanocrystallization within the heterogeneous structure was simply added to the habitual effect of H-2-dilution in the promotion of crystallization in the Si : H network. Using partial H-2-dilution in trivial amounts to the mostly He-diluted SiH4 plasma and combining their individual influences, highly conducting intrinsic nc-Si : H films were produced at high growth rate from (SiH4 + He + H-2)-plasma in rf PECVD and that introduces enormous technological promise for efficient utilization of the material in the fabrication of devices.