The growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum dots on patterned SiO2/Si(001) substrates by molecular beam epitaxy were studied. The hexagonally ordered Si holes with 30 nm thick SiO2 mask layer having ~25 nm diameter, ~40 nm center-to-center distance, and density of ~7 × 1010 cm-2, were formed using self-assembled diblock copolymer, composed of polystyrene and poly(methyl methacrylate) (PS-b-PMMA). The multiple Ge nuclei are selectively formed along the periphery of the individual Si holes and these nuclei subsequently coalesce forming single dot with an identical size of patterns. The strain of dots is relaxed up to 80%. The lattice planes of some Ge dots are found to be tilted from those of Si substrates. The Ge dots have dislocations at the interface with Si substrate even at the small size of ~25 nm, resulting from the limited elastic relaxation in the confined patterned structure.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics