Surface roughness and optoelectronic properties of intrinsic and doped nc-Si:H prepared by Rf-magnetron sputtering at low temperature

The correlation between the surface roughness and optoelectronic properties of a series of intrinsic and doped nanocrystalline silicon samples deposited by rf-magnetron sputtering at low temperature has been deduced from atomic force microscopy, spectroscopic ellipsometry, optical transmission and reflection and Raman spectroscopy measurements. Atomic force microscopy observations and spectroscopic ellipsometry analysis of the surface layers reveal that the Root Mean Square (rms) surface roughness for the doped samples increases with increasing sample thickness, while for the intrinsic samples we obtain lower rms surface roughness values which are found to be independent of the film thickness. The surface roughness is related to the microstructure of crystalline grains at the layer surface as verified by analysis of the experimental pseudo-dielectric function. However optical reflectance measurements obtained show that the film thickness affects the surface roughness, but not significantly the complex refractive index.