Ge dots self-assembling: Surfactant mediated growth of Ge on SiGe (118) stress-induced kinetic instabilities

The ordering of islands on naturally or artificially nanostructured surfaces is one of the most recent objectives among actual nanotechnology challenges. We show in this letter that, by a combination of two approaches, i.e., a two-step molecular beam epitaxy (MBE) deposition process and surfactant-mediated growth, we are able to obtain chains of nicely ordered ultrasmall islands of lateral size below 50 nm. The two-step MBE process consists of vicinal Si(001) surface self-patterning by SiGe growth instability and Ge dot ordering by subsequent Ge deposition on a SiGe template layer. The surfactant-mediated growth consists of submonolayer Sb deposition prior to Ge growth, in order to reduce the island size up to 25 nm. The best ordering of Ge islands is obtained when the island size matches the wavelength of the template layer