Overall elastic properties of polysilicon films: a statistical investigation of the effects of polycrystal morphology

In this paper we investigate the effects of polycrystal morphology on the overall properties of polysilicon. Focusing on two-dimensional representative volume elements (RVEs) of textured films, we numerically generate digital polycrystal morphologies through Voronoi tessellations and assume the in-plane orientation of the crystal lattice of silicon grains to be randomly distributed. First, we show how a regularization provision for the Voronoi tessellations, adopted in order to better match the grain boundary (GB) geometry featured by actual polysilicon films, affects the statistics of an internal length-scale which naturally emerges because of the presence of GBs. Second, we provide a numerical homogenization technique to estimate the overall in-plane elastic moduli of the polysilicon film and compare the outcomes with standard Voigt and Reuss bounds. Through this comparison, we furnish a way to also estimate the size of the RVE to get effective results. Third, through Monte Carlo simulations we investigate the effect of microstructural fluctuations on the scattering of the overall elastic moduli of polysilicon.We show that even when the RVE appears to be representative for a single polycrystal realization, the RVE might not be representative if one looks at the extreme values of the aforementioned scattered elastic moduli.