Simulation of hydrogen evolution from nano-crystalline silicon

The temperature dependent H-evolution from nano-crystalline silicon is simulated with molecular dynamics. The nano-crystalline silicon model consists of a heterogeneous dispersion of nano-crystallites in an amorphous silicon matrix. An excess H-density occurs at the nano-crystallite surface. Simulations find a low temperature evolution peak at 250–400 °C, where the H-evolution occurs from the surface of the nano-crystallite. In addition there is a higher temperature peak at 700–800 °C. The two-peak feature agrees with H-evolution measurements of H-diluted a-Si:H grown near the phase boundary of crystalline growth. We find that H is released into mobile molecular and bond-centered like configurations.