Effect of doping with M (M=Al, Pd, Ti, Ge) on the electronic structure and hydrogen diffusion behavior of amorphous silicon

Amorphous silicon (a-Si) models doped with Pd, Ge, Al, and Ti (a-Si/M) at three different doping ratios are generated using Ab initio Molecular Dynamics (AIMD) high-temperature annealing, followed by analysis utilizing first-principles method. The electronic structure calculations reveal strong interactions between Al, Ge and Si, while interaction between Pd, Ti and Si are relatively weak. Moderate doping of Pd and Ti can reconstruct the a-Si surface, reduce the adsorption energy of H on the surface, and increase the Si-Si atomic gap. This will greatly reduce the energy barrier for H to diffuse on the surface and to the subsurface.