Ion bombardment effects on the microcrystalline silicon growth mechanisms and structure

The role of ion bombardment in the growth mechanisms and the microstructure of microcrystalline silicon thin films produced by RF-PECVD is highlighted through the analysis of the effect of pressure and bias voltage applied to the RF electrode. The films are deposited on glass substrates by the standard hydrogen dilution of silane. It turns out that ion bombardment presents detrimental as well as beneficial aspects. In particular we show that high energy ions promote the nucleation of crystallites on glass substrates. Moreover, we show that after the nucleation phase the ion energy should be reduced to avoid damage to the bulk and the formation of an amorphised subsurface layer.