Local distribution of segregated Si on the hydrogen-treated Ge/Si(001) studied by STM

Intermixing effect between Si and Ge is the key issue to achieve precise composition control of the SiGe nanodevices. It has been known that hydrogen-rich condition at $\sim $300 °C induces segregation of Si to the surface layer of the Ge covered Si(001) surface, while Ge prefers to stay at the surface layer without hydrogen$^{1}$. The local distribution of Si and Ge on the Ge/Si(001) surface was investigated by STM to study the atomic process of this intermixing effect. We found that Si-H and Ge-H sites on the H-terminated Ge/Si(001) can be resolved using the empty-state imaging condition, which is similar to the recently-reported case of Cl-terminated Ge/Si(001)$^{2}$. Furthermore, it was found that the segregation of Si induced by the H-annealing produces significantly bright features beside the dimer-row vacancies (DVLs) in the empty state image of H-Ge/Si(001), in addition to the features coming from normal Ge-H and Si-H sites. The statistic analysis of these features revealed that the segregated Si atoms are mostly located at the brightest feature beside the DVLs, supporting the previously suggested model of intermixing process$^{1}$. $^{1}$ Rudkevich \textit{et al}., Phys. Rev. Lett. \textbf{81}, 3467 (1998). $^{2}$ Lin \textit{et al}., Phys. Rev. Lett. \textbf{90}, 046102 (2003).