Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7x7

Small amounts of Ge atoms are deposited on Si(111)-7×7 surfaces at room temperature (RT) and at 100 °C to clarify the initial adsorption sites using scanning tunneling microscopy. At RT Ge atoms are adsorbed at high coordination B_2 sites around the rest atoms, as predicted by Cho and Kaxiras [Surf. Sci. 396, L261 (1998)]. On one hand, at 100 °C Ge atoms are adsorbed on corner adatom sites. With increasing Ge coverage the corner sites are gradually occupied, followed by Ge adsorption at center adatom sites, resulting in Ge cluster growth with a size of the half unit cell