Session D40 - Poster Session I.
POSTER session, Monday afternoon, March 12
Exhibit Hall, Washington State Convention Center
Ge_1-xSi_x/Si heterostructure system has been intensively investigated because of its importance both for the materials science and for the technological application. The Ge growth on a clean Si(001) surface shows undesired features such as a rough surface due to the Stranski-Krastanow (SK) growth and a large interface mixing. Surface hydrogen is known to act as a surfactant for this system. It can change the growth mode from the SK mode to a layer-by-layer growth and improve the interface mixing. The origin of such H effects is, however, still unclear. To unveil the mechanism of the H surfactant effects, it is indispensable to know the Ge adatom behaviors on the H-terminated Si(001) surface. In this paper, we theoretically investigate the adsorption and diffusion of Ge atoms on the H/Si(001)-(2x1) surface by using first-principles calculations. The Ge atom deposited on the surface forms a Ge di-hydride at the dimer center, as a Si adatom does. Then, it exchange the site with a substrate Si atom with an activation barrier of as small as 0.75 eV to form a substrate Ge-Si dimer with an ad-Si dihydride. Although the Ge atom forms substrate Ge-Si dimer, it can diffuse along the dimer row by hopping from a backbond of a dimer to another.