A critical review of the available experimental data obtained under conditions relevant for the deposition of high quality material shows that: 1) The dominant channel of the deposition of microcrystalline silicon (“μc-Si”) is the fragmentation of SiH4 into SiH2 and H2 followed by fast insertion of SiH2 into the surface of the growing film. The rate determining step is the ion induced dehydrogenation of the surface of the growing film. 2) The SiH2 formation followed by fast insertion into another SiH4 forming Si2H6 is the dominant channel of silane decomposition during the deposition of a-Si. Adsorption of disilane at the surface of the growing film followed by its decomposition can explain the experimental data. The published data show that the contribution of the SiH3 radical to the commonly observed growth rates of ≥ 0.1nm/s is negligible.
The plasma parameters which control the deposition of a-Si and c-Si (μc-Si and epi-Si) are identified on the basis of experimental results, and their effect on the crystalline-to-amorphous transition is explained. Ion bombardment at energies below the displacement threshold has beneficial effect on the properties of the deposit as illustrated by electrical conductivity, gas incorporation, optical absorption and light scattering data.