Hydrogen passivation of silicon surfaces: A classical molecular-dynamics study

We present a computationally efficient classical many-body potential that is capable of predicting the energetics of bulk silicon, silicon surfaces, and the interaction of hydrogen with silicon. The potential includes well established models for one-component Si and H systems and incorporates a newly developed Si-H interaction. It is shown that the present model yields hydrogen diffusion barriers, hydrogen abstraction, and H-2 desorption reactions on silicon surfaces in excellent agreement with experiment and/or previous ab initio results. Derailed molecular-dynamics simulations an performed that elucidate the complex balance between adsorption and abstraction reactions during hydrogen passivation on Si(100) surfaces. We find a very high sticking coefficient of 0.6 for atomic hydrogen on clean Si(100)2X1 surfaces and provide a detailed qualitative and quantitative explanation for this prediction. Furthermore, we find that there are two efficient competing surface reactions of atomic hydrogen with monohydride Si surfaces. One is the Eley-Rideal abstraction of H-2 molecules, and the other one is adsorption. Additionally, adsorbed hydrogen on hydrogenated Si surfaces acts as a reservoir that can lead to complete passivation of Si surfaces despite the efficient creation of voids in the hydrogen layer by the abstraction.