Nano hard drives in range?

The formation of magnetic quantum dots is simulated in step flow models

"Result of a phase field simulation of growth spirals and mountains in epitaxial growth" © TU Dresden
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It sounds a bit like a dream of the future: saving hundreds of terabytes on the surface of a currently standard hard drive? But scientists from the EU project "Mag-Dot" are tracking this technology. They perform mathematical simulations on how to store data thousands of times more effectively on nanostructured media.

The trick is in the structure: Instead of the usual lithographic process today, the storage layers of an iron-platinum compound in the so-called MBE thin-film process (from the English "molecular beam epitaxy") are deposited on the wafer. Due to an as yet incompletely understood process of self-organization, so-called "quantum dots" are formed - tiny atom islands that can each store one bit of information through magnetic alignment.

Enigmatic quantum dot structures

At the Institute of Scientific Computing of the TU Dresden, the processes involved in the formation of such islands are mathematically simulated as part of the EU project "MagDot". The researchers want to find out what are the driving factors that influence the arrangement of the quantum dots, because so far it has not been possible to produce regular quantum dot structures. The scientists suspect that the self-assembly probably occurs by a mechanical stress of the few atoms thick layer on the substrate.

The simulation by discrete models, explains Institute Director Prof. Axel Voigt, is not sufficient for the complex consideration of self-organization. Finally, one wants to understand how the individual atoms behave, but also how they interact on the comparatively large substrate surface and arrange themselves into islands - a multi-scale problem. The Dresden scientists help him with step flow models; with discrete continuous calculation models, which are combined across scales. The enormous computing power required for such simulations is provided by the university's own Information Services and High Performance Computing Center.

The simulated data is experimentally verified by scanning tunneling and transmission electron microscopy. By varying the temperature in the fabrication of the quantum dots, mechanically biasing the wafers, or "pre-patterning" the substrate as it were, researchers want to understand what affects the formation of quantum dots, ultimately achieving a regular lattice-like arrangement. display

(idw - Technische Universität Dresden, 28.06.2007 - AHE)