How this can be done is described in an article to appear in the January issue of Nature Nanotechnology, with Philippe Caroff and Kimberly Dick as the main authors.
According to Professor Lars Samuelson, this is a breakthrough both in the development of nanowire growth, and in the understanding of the fundamental materials physics processes involved.
- The results achieved here establish our position in this area of science and technology and give our ambitions an increased credibility, he says. The useful applications will not be far away.
It has been known for a long time that most semiconductor materials used in nanowires, including the very interesting material Indium Arsenide (InAs) studied here, are affected by irregularities in the layer-by-layer stacking sequence. These affect the electronic and optical properties in uncontrolled ways, and are therefore undesirable.
But now Philippe Caroff and Kimberly Dick have shown that it is possible to control these variations in great detail, which can be used for the development of new functions in nanowires.
It is now possible not only to fabricate perfect, defect-free nanowires, but also to switch freely between different crystal types along the length of a single nanowire, to produce a, so-called, superlattice, but still using only one chemical compound (InAs).
- Two of the key parameters needed to control the crystal structure are nanowire diameter and the temperature at which they are fabricated. But there are in total at least 10-12 different parameters that must be controlled when producing the nanowires, says Kimberly Dick.Although this result has been demonstrated primarily for the binary compound InAs, it is believed that the mechanisms controlling the nanowire structure can be generally applied to related semiconductor materials used in nanotechnology.
With this technique it is also possible to grow highly regular nanowires with a perfect periodic facetted character.
Electron microscopy images show that the arrangement of atoms in the nanowire crystal exactly matches theoretical simulations. The electronic and optical properties of these wires have not been investigated yet but will be in the focus of theoretical as well as experimental studies.
The nanowires in this study had a typical diameter of 10-100 nanometers (one nanometer is one-millionth of one millimeter) and length of a few micrometers (one-thousandth of one millimeter).
The wires are produced by "baking" in an oven with a supply material in gas form, and grow from small microscopic gold "seeds". Kimberly Dick defended a PhD thesis last year containing many electron microscopy images of similar nanowires.
The researchers work within the Nanometer Structure Consortium (nmC) at Lund University to also find commercial applications for these nanowires in electronics and opto-electronics, such as for light-emission and solar cell applications.Lars Samuelsson could be contacted at
It is also reviewed in an article in Semiconductor Today: www.semiconductor-today.com/news_items/2008/DEC/LUNDUNIVERSITY_021208.htm
Mats Nygren | idw
Tracing aromatic molecules in the early universe
23.03.2017 | University of California - Riverside
New study maps space dust in 3-D
23.03.2017 | DOE/Lawrence Berkeley National Laboratory
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
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Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
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