Adsorption of hydrogen on a Ge covered Si(100) surface

In the present work we study hydrogen adsorption on Ge layers deposited by molecular beam epitaxy (at 600 K) on a Si(100) surface using temperature programmed desorption (TPD), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and work function measurements. The hydrogen TPD spectra exhibit a multipeak structure which gradually changes with increasing Ge coverage (up to 3 ML). Using Redhead's theoretical thermal desorption curves for the shape of the individual constituents of the H-2 TPD spectra, we have found five different states (beta(1)-beta(5)) Accepting that hydrogen desorption occurs through a transition state localized near a single atom, the behaviour of the deconvoluted peaks upon increasing Ge and hydrogen coverages, suggests the existence of long and short range effects of deposited Ge. The work function changes, observed upon hydrogen exposure and after mild annealing, give strong evidence of an initial uniform hydrogen adsorption on a Ge/Si(100) surface and migration from Ge to Si related sites, during the annealing procedure.