™™| 07/29/10 | |||
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Technology name:
Technology description: Researchers at the University of Arkansas have developed a solution to the problem of producing a specific pattern of Q-dots. The method uses a nano-indenter to produce a small, light “dent” in the atomic structure of a gallium arsenide (GaAs) substrate. By impressing the GaAs lightly (ultralow load) it is possible to produce areas of strain in the GaAs lattice – changing the lattice constant of the material.
The nucleation of the Indium “Q-dots” is then preferred at the exact site of the changes in the lattice constant brought on by the nano-indentation. By using a square shaped nano-indenter tip, nucleation sites can be produced at each of the four corners of the indentation. The Q-dots can then be “grown” through “self-assembly” by using molecular beam epitaxy technology. Patterns of Q-dots can be produced by precisely locating nano-indentations and then growing Q-dots at those locations.
A further key apect is growing the Q-dots on the side of the GaAs substrate that is opposite of the indentation, and selectively etching the “backside” such that the strain fields created by the nano-indentation are just barely exposed on the surface. This technique prevents dislocations in the lattice from migrating into the Q-dot itself, allowing for a coherent and electrically/optically stable Q-dot structure.
See also:
Taylor, C., Prince, R., Riester, L., Salamo, G., Oh Cho, S., Malshe, A., Characterization of ultra-low-load (mN) nanoindents in GaAs (100) using a cube corner tip, Journal of Smart Materials and Structures 14 (2005) p. 963-970.
Taylor, C., Stach, E., Malshe, A., Salamo, G. Nanoscale Dislocation Patterning by Ultralow Load Indentation, Applied Physics Letters, 87, 073108 (2005). | |||