How nanowires can be formed

Nanowires are believed to be important elements in several different areas, such as in future generations of transistors, energy efficient light emitting diodes (LEDs) and solar cells.

The fact that it is possible to affect how nanowires are formed and grow has been known for a long time. What researchers have now been able to show is what needs to be done to give the nanowires a particular structure.

The gound-breaking discovery includes showing how nanowires grow, and affect the formation of different atomic layers, by using a powerful microscope and theoretical analysis.

"We now have on tape the events that take place, and what is required to be able to control the nanowire growth," says Daniel Jacobsson, former doctoral student at the Lund University Faculty of Engineering, and currently a research engineer at the Lund University Centre for Chemistry and Chemical Engineering.

The team wanted to understand how nanowires grow, and chose to film them though an electron microscope. The article in Nature is about these films, which show nanowires made from gallium arsenide and composed of different crystal structures.

"The nanowires grow through a self-assembly process which is spontaneous and hard to control. But if we can understand how the nanowires grow, we can control the structures that are formed in a more precise way, and thereby create new types of structures for new fields of application," says Daniel Jacobsson.

At the Centre for Chemistry and Chemical Engineering in Lund, a world-leading "super microscope" is under construction, which will be able to show, in high resolution, how atoms are joined together when nanostructures are formed.

"In our Nature article, we show how dynamic the growth of nanowires really is. Once the new microscope is in place, we hope to be able to provide even more details and expand the scope of materials studied.

Both the current results, and hopefully those to come, are important for an even more exact formation of nanowires for various applications," says Professor Kimberly Dick Thelander.

Facts/Study about nanowires

Nanotechnology could be seen as engineering of functional systems at the atomic scale, which illustrates the growth of nanowires, where different atomic layers are stacked on top of each other. In the study Interface Dynamics and Crystal Phase Switching in GaAs Nanowires, the researchers were able to monitor in real time where each new atomic layer is placed in a growing nanowire, and explain why they place themselves where they do. The study shows that it is possible to control the position of each new atomic layer, and was conducted in collaboration with researchers at the IBM T. J. Watson Research Center, USA, and Cambridge University, UK.

Facts / Nanowires

A nanowire is an extremely thin wire with a diameter equal to one thousandth of a human hair. They are made out of many different materials, for example metals such as silver and nickel, semiconductor materials such as silicon and gallium arsenide, and insulating material such as silicon oxide.

Nanowires are useful because they enable the formation of complex structures with many chemical compounds, and sometimes different atomic arrangements. Nanowires are usually made out of single crystals, and the specific atomic arrangement is what determines the structure of the crystal.

Every new type of complicated structure -- whether it be a combination of different materials or a new way of joining atoms together -- involve new properties and thereby different applications in areas such as electronics and lighting.