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Using very high Ar-dilution to the SiH4 plasma, good quality amorphous Si:H films could be obtained at very low rf power. The a-Si:H film, prepared at a very low deposition rate of ∼10 Å/min, exhibited a σPh∼1×10−4 S cm−1, σPh/σD∼105, a notably wide optical gap of 2.10 eV and a very good stability against thermal annealing effects with reasonable light induced degradation. At higher rf power undoped μc-Si:H films were prepared with a high σD∼1×10−4 S cm−1, at a deposition rate of 30 Å/min from <1 sccm of SiH4. Micrograins were identified with several well-defined crystallographic orientations. However, porosity in the grain boundary zone contributed a significant amount of adsorbed effects on the electrical properties. At very high powers, the growth of a columnar network structure was demonstrated. Long-range structural relaxation permitted by the non-rigid and heterogeneous network structure associated with the physical vapor deposition-like growth at the microcrystalline-transition state, has been identified as the origin of nucleation to the Si network and microcrystallization at higher power. It is proposed that Ar* in the Ar-diluted plasma provides the energy required for nucleation and grain growth during microcrystallization, and plays an analogous role as atomic H does during chemical annealing in H2-diluted plasma.

Film growth precursors in a remote SiH 4 plasma used for high-rate deposition of hydrogenated amorphous silicon J.Role of the surface roughness in laser induced crystallization of nanostructured silicon films Hydrogenated microcrystalline silicon thin films have been prepared by the rf glow discharge method using argon as a diluent of SiH 4 to achieve a high growth rate. c-Si:H film having conductivity ϳ10 Ϫ5 S cm Ϫ1 was achieved at a deposition rate of 36 Å/min at a moderate power density of 90 mW/cm 2 , without hydrogen dilution. Micrograins were identified with several well defined crystallographic orientations. Inhomogeneity and porosity at the grain boundary zone have a significant effect on the electrical properties of the films due to adsorption when exposed to atmosphere. However, by adding hydrogen to the Ar-diluted SiH 4 plasma, a homogeneous and improved network structure without having any effect of adsorption was obtained at a reduced deposition rate. Highly conducting ( D ϳ10 Ϫ3 S cm Ϫ1 ) undoped c-Si:H film was prepared at a deposition rate of 15 Å/min having 90% crystalline volume fraction. The energy released by the de-excitation of Ar* in the plasma initiates rapid nucleation in the Si network and atomic hydrogen in the plasma helps in the defect elimination, structural reorientation, and grain growth.

Hydrogen plasma treatment of stacking layers in a layer-by-layer (LBL) growth scheme effectively modulates the network structure from the surface into the bulk through the growth zone by abstraction of hydrogen from the Si:H matrix. It is an efficient way of reducing the microcrystalline transition layer so that virtual saturation of the crystallization may be obtained at a significantly low thickness of the sample compared to that obtained by a continuous mode of deposition. The growth of a highly conducting undoped µc-Si:H film at a stacked layer thickness of ∼650 Å is described. The film has a dark conductivity, σD, of ∼4×10-3 S·cm-1 and exhibits a very high crystallinity, as determined by Raman scattering and transmission electron microscope studies.

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