We have been successful in fabricating as-deposited microcrystalline silicon (mu c-Si) on polyethersulfone and polyethylene terephthalate substrates and, have assessed the characteristics of the Si films. We note that 13.5 MHz radio-frequency (rf) substrate bias during electron cyclotron resonance plasma deposition can be used to tailor the characteristics of these as-deposited mu c-Si microcrystalline silicon films on the polymer substrates. As the rf substrate bias is applied and increased, as-deposited Si films loose their degree of crystallinity. At the same time, the activation energy of the Si film tends to be decreased and the intensity of the film photoluminescence (PL) is enhanced. Part of this increased PL intensity that is found with the addition of rf substrate bias occurs in a PL band at about 0.9 eV. This PL band in Si films may be attributed to the amorphous silicon (a-Si) materials.