Researchers move an atom inside a crystal and investigate its function

Jan 28, 2014
The first to move an atom inside a crystal: Alexander Weismann and Hao Zheng in front of the scanning tunneling microscope Credit: Wimber/CAU

Nanotechnology is a thriving science. Parts for computers for example are becoming smaller and more precise by the minute. One of the most efficient computers would be the so-called quantum computer. Up to now, its existence has been merely a concept that is based on the laws of quantum mechanics. Here, the ability to control the state of single atoms is decisive. For the first time ever, scientists of Kiel University have managed to move single atoms vertically inside a crystal. This is important for the further development of nano structures. Simultaneously, the physicists found a method for measuring a transistor-like behaviour of single atoms. These findings have recently been published in the scientific magazine Nature Communications (January, 3rd, 2014) as well as in the renowned Physical Review Letters.

When manufacturing nano structures, the understanding, analysing and handling of materials present major challenges. A widely used and investigated material for piezo-, micro-, and optoelectronic devices is (ZnO). As a semiconductor it is built into light-emitting diodes (LED) and LCD-displays. Also, it is used as nanowires in electrical measurement technology. Some of its properties – such as the conductivity of the pure material – have to date not been understood. A major step towards solving this mystery was recently made by Dr. Hao Zheng, Dr. Alexander Weismann and Professor Richard Berndt of the Institute of Experimental and Applied Physics at Kiel University. While experimenting at the Collaborative Research Center "Magnetoelectric Composites – Future Biomagnetic Interfaces," Zheng was analysing zinc oxide with the scanning tunnelling microscope (STM). This device is able to image crystals on an atomic scale. He discovered circular structures in the otherwise irregular surface. "We found that they are a result of zinc that were incorrectly positioned in the crystal lattice", says Zheng.

Each of the discovered atoms featured two rings – a clear proof that it can donate two electrons. "We studied all scientific literature to find out that no-one had so far proven why zinc oxide is conductive. The logical conclusion was that the reason must lie within the newly found zinc atoms, which are naturally occurring in this material."

Further research led Dr. Zheng to discover that the ring's size could be varied while being exposed to experiments in the scanning tunnelling microscope. He asked for the help of his colleague Weismann, who is an expert for model calculation. "The calculation hinted that the diameter of the ring revealed something about the depth of the atoms below the surface", says Weismann. With this it was clear that Zheng had discovered a way to change the position of an atom by a single atom's width. "This is the first time a single atom is controllably moved within a crystal with atomic precision", Weismann stresses. "This ability will be helpful when designing nano structures in laboratories."

Along with their other findings, the scientists of Kiel University noted a behaviour that was similar to that of transistors. This component, which is used in computers by the million, usually requires three contact electrodes. When working with nano structures such as atoms, which measure only 0.3 nanometers, three electrodes would inevitably cause a short-circuit. "With the help of the STM we have discovered a method that only needs two electrodes, one of which is movable." This also is a major step for the handling of .

Explore further: Supercomputer used to simulate 3,000-atom nano device

More information: Zheng, H. et al. Tuning the electron transport at single donors in zinc oxide with a scanning tunnelling microscope. Nat. Commun. 4:2992 DOI: 10.1038/ncomms3992 (2014). http://www.nature.com/ncomms/2014/140103/ncomms3992/full/ncomms3992.html

Related Stories

Supercomputer used to simulate 3,000-atom nano device

Jan 14, 2014

Fujitsu Laboratories announces that it has successfully simulated the electrical properties of a 3,000-atom nano device – a threefold increase over previous efforts – using a supercomputer. At the nanoscale ...

Building quantum states with individual silicon atoms

Apr 03, 2013

(Phys.org) —By introducing individual silicon atom 'defects' using a scanning tunnelling microscope, scientists at the London Centre for Nanotechnology have coupled single atoms to form quantum states.

Two-proton bit controlled by a single copper atom

Jan 16, 2014

Just a single foreign atom located in the vicinity of a molecule can change spatial arrangement of its atoms. In a spectacular experiment, an international team of researchers was able to change positions ...

Single-atom transistor is 'perfect'

Feb 19, 2012

In a remarkable feat of micro-engineering, UNSW physicists have created a working transistor consisting of a single atom placed precisely in a silicon crystal.

Recommended for you

First direct observations of excitons in motion achieved

Apr 16, 2014

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton ...

User comments : 0

More news stories

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...