DISTRIBUTION OF PORES IN A-SI1-XCX-H THIN-FILMS

The aim of this paper is to compare the optical, compositional and mor phological properties of a-Si1-xCx:H films deposited by plasma enhance d chemical vapour deposition (PECVD) using different mixtures of silan e (SiH4) and methane (CH4) under minimum attainable deposition pressur e. Films deposited at lower silane flow present a higher carbon conten t and larger optical gap. The morphology of the films was investigated by small-angle X-ray scattering (SAXS) using two different light sour ces: (i) conventional tube and (ii) synchrotron radiation. The analysi s of the data from both experiments was performed in order to determin e a size distribution for spherical pores. The results obtained with b oth light sources are consistent: the increase in the CH4 concentratio n implies broader size distribution functions, with an increase of the pore size up to 10 nm. Larger pores are found in films deposited at l ower silane flow. For all samples, the density of the smaller pores do minates the size distribution. The relative microvoid density is not p roportional to the carbon concentration but presents a maximum for the low carbon content films.