Thin nanowires could in electronics, optics and medical help in the coming years to make mobile phones or computers and compact to achieve a particularly high screen resolution. An international research team led by physicist Professor Christina Scheu LMU is successfully able to observe the formation of alumina nanowires at atomic resolution and in real time.
In this case, the researchers found that the self-catalytic growth of aluminum wires in a two-stage process occurs, the wire being erected along its longitudinal axis, layer by layer. The unprecedented move, the researchers recorded using a high-resolution electron microscope. Be “Our studies are important for understanding the growth of nanowires of different materials and then consciously manage this change and can be,” said Scheu, whose research in the cluster of excellence Nanosystems Initiative Munich (NIM) encouraged. (Science online, 21 October 2010).
Wafer-thin nanowires with diameters of less than 50 nanometers, which corresponds to one billionth meter, have the potential to electronic devices – such as mobile phones and computers – to make the future more compact. Their growth can be influenced only in cases when the research underlying the development process in detail understands. Most nanowires grow in a so-called gas-liquid-solid process (Vapor-Liquid-Solid Growth or VLS).
Here, the growth necessary atoms pass from the gas phase above the liquid phase to a solid state, which then forms the nanowire. “Nanowires made of silicon for example grow by itself solve the silicon atoms in a drop of liquid gold and then move towards the interface of the nanowire to which they attach to it,” said Professor Christina Scheu from Department of Chemistry and the Center for Nanoscience (CeNS).
Previously it was unclear what would happen if the liquid phase required for growth can not solve the type of atom can. “Our system is exactly the case,” said Scheu, under whose direction focused an international team of researchers from Korea, Israel, USA and Germany with the issue. “The growth of the alumina nanowires used in liquid Al-drops can hold at high temperatures, no oxygen.” The researchers therefore investigated the impact this has and led at 750 degrees Celsius experiments in a transmission electron microscope at the Max- Planck Institute for Metals Research in Stuttgart is located.
These tests were able to observe the atomic processes during growth of the alumina wires. It was found that the self-catalytic growth of nanowires in a two-step process takes place. The so-called three phase points – or triple points – between the liquid phase, gas phase and solid phase are initially formed small crystal facets and then dissolved. “If the crystal facets grow in length, oxygen is released, which can be installed along the interface between liquid and nanowire,” says Scheu. “For the nanowire grows by one atomic layer.”
These transactions were recorded in a real-time video. “Without these high-resolution images would have the atomic processes at the two-stage growth of aluminum wires can not even explain,” says Scheu. “In addition, we would have missed the central role of the triple points that have been often viewed as rigid.” This detailed understanding of the formation of nanowires is a prerequisite for the deliberate manipulation of its growth. Shyness and her team do in subsequent trials, we explain the growth, structure and properties of nanowires made of other materials.
