Study of growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum dots on nanometer-scale patterned SiO2/Si(001) substrates

Abstract

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 similar to 25 nm diameter similar to 40 nm center to center distance and density of similar to 7 x 10(10) 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 peripery of the individual Si holes and these nuclei subsequently coalesoe 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 substrate even at the small size of similar to 25 nm resulting from the limited elastic relaxation in the confined patterned structure. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim