Shedding light on the growth of amorphous, polymorphous, protocrystalline and microcrystalline silicon thin films

We focus here on a study of the growth of polymorphous and protocrystalline silicon materials with respect to the well-established amorphous and micro crystalline silicon. Protocrystalline films correspond to a slow crystallis ation process, in which the films grow densely in the first monolayers, but their porosity and roughness increase with thickness, allowing the nucleat ion of crystallites, and finally the formation of a microcrystalline phase. On the contrary, polymorphous films remain dense, independent of their thi ckness. The control of the temperature gradient between the RF electrode an d the substrate holder allows a switch from microcrystalline to polymorphou s silicon growth, which strongly supports our hypothesis of polymorphous fi lms being formed by simultaneous contributions of silicon radicals and clus ters to the growth. (C) 2001 Elsevier Science B.V. All rights reserved.