The microstructure of epitaxially grown self-assembled Ge islands on patterned SiO2 Si substrates was analyzed using high resolution transmission electron microscopy. The Ge islands were grown by molecular beam epitaxy on hexagonally ordered Si hole arrays with ∼25 nm diameter and ∼40 nm center-to-center distance, which are covered by 30 nm thick SiO2 mask layer patterned using self-assembled diblock copolymers. The Ge islands nucleate preferentially at the edge of overetched Si surface, and subsequently grow selectively on Si surface as opposed to SiO2 surface with increasing coverage. The lattice planes of some Ge islands are tilted from those of Si substrates. This is believed to be the reason for the observed misalignment of moiŕ fringes. The diameter of the Ge islands is identical to that of Si holes for large Ge coverage due to the selective growth behavior. These islands are found to have dislocations at the interface with the Si substrate. These results highlight the important microstructural issues and growth behavior of quantum dots on patterned substrates.
Bibliographical noteFunding Information:
The authors acknowledge the support of the Microelectronic Advanced Research Corporation (MARCO) and its Focus Center on Functional Engineered Nano Architectonics (FENA). This work was supported from the National Program for Tera-level Nano Devices, one of the 21st Century Frontier R&D Programs funded by the Korean Ministry of Science and Technology.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)