Selective growth of Ge islands on nanometer-scale patterned SiO ₂/Si substrate by molecular beam epitaxy

The authors studied the selective growth of Ge islands by molecular beam epitaxy on Si(001) covered with nanometer-scale patterned SiO ₂ mask generated using self-assembled diblock copolymer. Selective growth is made possible by Ge adatoms desorbing from the SiO ₂ surface as well as diffusing into the exposed Si area. For the Ge coverage of 2 nm, multiple islands are observed along the periphery of individual exposed Si areas. At 3.5 nm coverage, the coalescence of small islands with significant strain relaxation becomes evident. The ramifications of the multiple islands morphology and their coalescence on potential device applications are discussed.