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 under standing gas-source growth, as the presence of hydrogen on the surface duri ng gas-source growth of silicon and germanium dramatically changes the kine tics of growth and the morphology of the growth surface. We have used a com bination of hot scanning tunnelling microscopy experiments and computationa l modelling, with the two techniques inter-relating, to investigate this sy stem. By comparison with experimental and ab initio results, we have shown that our semi-empirical tight-binding code is sufficiently accurate to calc ulate diffusion barriers on the surface, while being efficient enough to be used in large simulations, such as that of the interaction of hydrogen wit h 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 o f the behaviour of hydrogen on the Si(001) surface.