Formation of ultrahigh density Ge nanodots on oxidized Ge/Si(111) surfaces

Ge nanodots with a typical size of ∼4 nm and ultrahigh density (>1012 cm−2) were grown on ultrathin SixGe1−x oxide films made by oxidizing Ge wetting layers grown on Si (111)–(7×7) surfaces. The density of the nanodots was independent of the Ge deposition rate, indicating that the chemical reaction between Ge atoms and the oxide films determined the nucleation of Ge nanodots. The size and density of Ge nanodots grown on the ultrathin SixGe1−x oxide films depended on the growth temperature and deposition amount. These dependences indicate that we can form the Ge nanodots with ultrahigh density controllably by using ultrathin SixGe1−x oxide films.