Hydrogen-surfactant mediated growth of Ge on Si(001)

The role of hydrogen in the growth of Ge on a Si(001)-(2 X I) surface was studied by scanning tunneling microscopy and medium energy ion scattering spectroscopy. The adsorbed hydrogen was found to (i) increase the number of equilibrium adsorption sites, (ii) lift the diffusion anisotropy, and (iii) lower the diffusivity for Ge adatom, as suggested by the recent first principle calculation. With a dynamically supplied atomic hydrogen flux of similar to 2 monolayers/s, we achieved layer-by-layer growth by preventing growth of the hut cluster beyond the known critical thickness. The 10.0 monolayer Ge layers grown with hydrogen surfactant are strained, while those without it are relaxed.