Effect of Hydrogen on the Microstructure Evolution of Nanocrystalline Silicon

Abstract

We have studied the effect of hydrogen on the microstructure evolution of  nanocrystalline silicon. We have performed molecular dynamics simulations to  identify the role of hydrogen on the nanocrystalline silicon recrystallization  phenomena. It requires an accurate description of any relevant atomic scale feature.  We have taken advances in computer modeling of nanocrystalline silicon and the  development of quantitative analysis tools. We have characterized the microstructure  evolution of nanocrystalline silicon by varying both the crystallinity and the hydrogen  content. We have estimated the rate of recrystallization as a function of the  hydrogeneration and showed that the boundary mobility decreased exponentially  with hydrogen due to the occurrence of clustering and to the accumulation of the  hydride at the boundaries. We have studied the atomistic details of the elementary  recrystallization process investigating the ability of dissolved hydrogen to slow down  the mobility of the amorphous crystalline boundaries. The effect is enhanced by  increasing the hydrogen content with a recrystallization rate that decreased  exponentially with hydrogen concentration. We found that at low concentration the  hydrogen tended to migrate from the crystal phase to amorphous one directly  affecting the thickness of the grain boundaries and increased their effective interface.