engleski

Structural Analysis of amorphous-nanocrystalline silicon thin films by Grazing Incidence X-ray Diffraction

Amorphous-nanocrystalline silicon thin films are promising material for photovoltaic application in new generation solar cells due to good optical properties influenced by structure. It consists of nanometer-sized crystalline silicon grains embedded in amorphous silicon matrix. The a-nc-Si: H samples 50-300 nm thick were deposited by Plasma Enhanced Chemical Vapor Deposition using mixture of silane and hydrogen as working gas on the top of thin a-Si:H layer previously deposited on the glass substrate. The structure of a-nc-Si:H was examined by Grazing Incidence X-ray Diffraction (GIXRD). The experiment was done at MCX beam line at synchrotron Elettra in Italy using 8 keV X-ray beam. The scattered intensity was obtained for several values of angle of incidence starting from critical angle for total external reflection for silicon in order to probe samples at different depth below the sample surface. Obtained diffractograms consist of crystalline silicon Bragg peaks superimposed on wide contribution characteristic for amorphous silicon. From the c-Si peak profile were obtained information about nanocrystals size distribution, crystalline/amorphous phase volume fraction, stress and strain. Obtained structural results were compared with the results obtained by High-Resolution Transmission Electron microscopy and correlated with the optical properties in the wavelength range relevant for solar cells. A possible application is discussed.

HRTEM; XRD; solar cells

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