Influence of the energy density on the structure and morphology of polycrystalline silicon films treated with electron beam

Microstructures of electron beam remelted polycrystalline silicon films (20 μm thickness) deposited on a borosilicate glass solar cell absorber with a tungsten inter layer were investigated. It was found that WSi2 compound was formed in both the tungsten/silicon interface and the grain boundaries of the silicon. The wetting and adhesion between the silicon melt and substrate were enhanced by the formation of WSi2 compound. The electrical properties of the solar absorber were deteriorated by the tungstendisilicide interlayer. Because of the fast melting and cooling of the silicon film, the silicon film was solidified in a non-equilibrium manner due to the fast cooling rate during the EB remelting. Microstructural analysis indicated that the surface morphology of the film was affected by the EB energy density used in the remelting process. The capping layer became smooth and continuous and the number of pinholes was reduced when the EB energy density was increased. The deposited films exhibited large voids in the outmost surface layer and more WSi2/Si eutectic crystallites in silicon layer and the WSi2 layer became thicker if the EB energy density was too high.