engleski

Analysis of silicon amorphous/nanocrystalline multi-layers by GISAXS and GIWAXS

Amorphous/nanocrystalline silicon thin film multilayers are promising structures for high efficient thin film solar cells. Their optical and opto-electrical properties and consequently efficiency are critically dependent on the nanocrystals size distribution and volume fraction. Samples deposited by plasma enhanced chemical vapour deposition were examined by Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Grazing Incidence Wide Angle X-ray scattering (GIWAXS) at the SAXS beamline at the Synchrotron Elettra, Trieste, using a setup adjusted to study objects with sizes in the range from 1-100 nm The size and shape of the nanocrystals were calculated from the horizontal and vertical sections of 2D GISAXS pattern while the in-depth analysis of the samples was done by variation of the grazing incidence angle. The thickness of the layers was estimated from interference fringes. The size of the nanocrystals varied between 2 and 20 nm with a non-uniform in-depth distribution. The results agreed well with those obtained by high-resolution electron microscopy and Raman spectroscopy for smaller crystals and crystal fraction up to some 30 volume %. The disagreement for larger crystals and higher crystallinity was attributed to strain effects. The advantage and disadvantage of each of the methods used for the analysis of the actual structures are discussed.

amorphous-nanocrystalline silicon; GISAXS; GIWAXS

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