An experimental-theoretical study of the behaviour of hydrogen on the Si(001) surface

An understanding of the dynamics of hydrogen on Si(001) is crucial to understanding gas-source growth, as the presence of hydrogen on the surface during gas-source growth of silicon and germanium dramatically changes the kinetics of growth and the morphology of the growth surface. We have used a combination of hot scanning tunnelling microscopy experiments and computational modelling, with the two techniques inter-relating, to investigate this system. By comparison with experimental and ab initio results, we have shown that our semi-empirical tight-binding code is sufficiently accurate to calculate diffusion barriers on the surface, while being efficient enough to be used in large simulations, such as that of the interaction of hydrogen with step edges. The behaviour of hydrogen has been investigated for diffusion along dimer rows, from one end of a dimer to the other, across dimer rows, down steps and away from a defect, with good agreement being found between measured and modelled diffusion barriers. We can now give a full account of the behaviour of hydrogen on the Si(001) surface.