Nanostructure characterization of nanocrystalline Si thin films by using small angle X-ray scattering (SAXS)

Nanocrystalline Si (nc-Si) films attract special interest from the point of view of the possibility of higher conversion efficiency compared to amorphous Si films. To investigate this possibility, it is necessary to know the nanostructure such as mean diameter and size distribution. Until now, transmission electron microscopy (TEM) and Raman analysis are used for this purpose. However, these methods have problems in determining the size; the observed region of TEM is restricted to several hundred nanometer, and the size was estimated based on a strong confinement model for Raman analysis despite the fact that the validity of this model has not been proved yet. In this paper, we report the determination of the average diameter and the size distribution of nc-Si films by using small angle X-ray scattering measurements (SAXS). We found that the model of Raman analysis used until now is not appropriate to determine the size of nanostructure. Based on SAXS results, we show a correct relation between the average diameter and the peak shift of Raman spectrum.