Jan 17, 2013
Nanosphere lithography pit pattern provides template for 3D densely ordered Ge QD crystals
Scientists from Fudan University, China, have fabricated 3D densely ordered Ge quantum dot crystals (QDCs) on nanosphere lithography (NSL)-patterned Si (001) substrates. By precisely controlling and optimizing the epitaxial growth parameters, up to 10 layers of 3D highly ordered and closely spaced Ge quantum dots were obtained with lateral and vertical periodicities of 100 and 7 nm, respectively.
NSL is a useful patterning technique for fabricating periodically ordered nanostructures. Large-area patterns can be easily obtained through self-assembled nanospheres, and the periodicity and the size of the nanopits can be adjusted using different process parameters.
Results obtained by atomic force microscopy and cross-sectional transmission electron microscopy show that 3D ordering was achieved in the Ge QDCs with an areal dot density of 1.2 × 1010 cm–2, and that the lateral and the vertical interdot spacing were ∼10 and ∼2.5 nm, respectively.
Thanks to the small inderdot spacings, the samples are particularly suitable for investigating the behavior of coupled quantum dot ensembles and related device applications.
The study demonstrates further progress in site-controllable growth of high-density ordered nanostructures. NSL pit-pattern assisted growth of Ge quantum dots is also applicable for other material systems, such as InGaAs and InP quantum dots.
More details can be found in the journal Nanotechnology.
About the author
The study was conducted by researchers from the State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai, China. The team’s work focuses on the growth and physical properties of Si-based low-dimensional materials, which includes the nanopatterning and site-controllable growth of Si/Ge nanostructures through molecular beam epitaxy (Riber Eva 32). Y J Ma is a PhD student in physics at the University of Fudan. He performed the patterning, the MBE growth and the atomic force microscopy experiments. The transmission electronic microscopy analysis was supported by Y Q Wu, a postdoc in materials engineering at the Center for Microscopy and Microanalysis, The University of Queensland, Australia. Prof. Z M Jiang is head of the nanopatterning and site-controllable growth group based in Fudan and guides the project. Prof. Z Y Zhong and Prof. X J Yang are research leaders in the group, with expertise in the nanofabrication and epitaxial growth of Si/Ge. Mr. Y. L. Fan is a senior engineer in physics department at the University of Fudan.