Tag Archives: Test & measurement

Moving silicon atoms in graphene with atomic precision

ScienceDaily – Richard Feynman [2, 3, 4, 5] famously posed the question in 1959: is it possible to see and manipulate individual atoms in materials?

For a time his vision seemed more science fiction than science, but starting with groundbreaking experiments in the late 1980s and more recent developments in electron microscopy instrumentation it has become scientific reality. However, damage caused by the electron beam is often an issue in such experiments.

Besides being beautiful physics, the findings open promising possibilities for atomic-scale engineering: “What makes our results truly intriguing is that the bond flip is directional — the silicon moves to take the place of the carbon atom that was hit by a probe electron,” explains Toma Susi, physicist and FWF Lise Meitner Fellow at the University of Vienna. more> http://tinyurl.com/phra9ao

Fluid mechanics suggests alternative to quantum orthodoxy

ScienceDaily – The system by Yves Couder and Emmanuel Fort consists of a bath of fluid vibrating at a rate just below the threshold at which waves would start to form on its surface. A droplet of the same fluid is released above the bath; where it strikes the surface, it causes waves to radiate outward. The droplet then begins moving across the bath, propelled by the very waves it creates.

“This system is undoubtedly quantitatively different from quantum mechanics,” John Bush says.

“It’s also qualitatively different: There are some features of quantum mechanics that we can’t capture, some features of this system that we know aren’t present in quantum mechanics. But are they philosophically distinct?” more> http://tinyurl.com/o4kcmpf

Postcards from the photosynthetic edge

By Lynn Yarris – Photo-oxidation of water by photosystem II is responsible for most of the oxygen in Earth’s atmosphere.

At the core of photosystem II is a manganese-calcium (Mn4Ca) metalloenzyme complex that when energized by solar photons catalyzes a four photon-step cycle of oxidation states (S0-to-S3) that ultimately yields molecular oxygen. Scientists need to observe intact x-ray crystallography of the Mn4Ca ion in action but the molecule is highly sensitive to radiation.

The LCLS (Linac Coherent Light Source) is the world’s only source of x-rays capable of providing femtosecond pulses at the high intensities that allow intact photosystem II crystals to be imaged before they are destroyed by exposure to the x-ray beams. more> http://tinyurl.com/nlxrcf8

When particles fall left and right at the same time

ScienceDaily – It takes only a slight disturbance for a pencil standing on its tip to fall in one direction or another.

In the quantum world it is possible in principle for particles of a system to fall both left and right at the same time. Differentiating this “and” state — the quantum entanglement of particles — from the classical “or” is an experimental challenge.

The Heidelberg researchers used a gas of approximately 500 atoms at a temperature of 0.00000001 Kelvin above absolute zero. After a short time a system with a high degree of quantum entanglement emerged.

To be able to experimentally verify this “and” state and its unique quantum mechanical properties, the team had to create a large number of these atomic systems under the same conditions and with different settings of the lab setup. more> http://tinyurl.com/ncesmkj

Getting a charge out of water droplets

By David L. Chandler – In attempting to develop an improved heat-transfer surface to be used as a condenser in applications such as power plants—that droplets on a superhydrophobic surface convert surface energy to kinetic energy as they merge to form larger droplets.

This sometimes causes the droplets to spontaneously jump away, enhancing heat transfer by 30% relative to other techniques.

They later found that in that process, the jumping droplets gain a small electric charge—meaning that the jumping, and the accompanying transfer of heat, could be enhanced by a nearby metal plate whose opposite charge is attractive to the droplets.

Now the researchers have shown that the same process can be used to generate power. more> http://tinyurl.com/qdf7oot

Swiss cross made from just 20 single atoms

R&D – Ever since the 1990s, physicists have been able to directly control surface structures by moving and positioning single atoms to certain atomic sites.

A number of atomic manipulations have previously been demonstrated both on conducting or semi-conducting surfaces mainly under very low temperatures.

However, the fabrication of artificial structures on an insulator at room temperature is still a long-standing challenge and previous attempts were uncontrollable and did not deliver the desired results.

In this study, an international team of researchers around Shigeki Kawai and Ernst Meyer from the Department of Physics at the University of Basel presents the first successful systematic atomic manipulation on an insulating surface at room temperatures. more> http://tinyurl.com/qgw3gcy

Optimizing Graphene Characterization

By Lishan Weng – Before 2004, when Geim and Novoselov demonstrated the existence of graphene, a single-atomic-layer-thick crystal of carbon, physicists didn’t believe such a substance could exist. Since then, graphene has attracted tremendous research interest because of its exceptional physical and electrical properties, including remarkably high electron mobility at room temperature, high transparency, very high thermal conductivity and superior mechanical strength.

Graphene is highly conductive, so measured voltages are low. The results (Figure) show the longitudinal resistance of the graphene layer as a function of the silicon substrate. They demonstrate graphene’s ambipolar nature; that is, that it conducts when either electrons or holes are induced into the material. The large slope on each side of the peak indicates a rapid decrease in resistance as the magnitude of the gate voltage increases, which offers evidence of graphene’s high carrier mobility. more> http://tinyurl.com/pvkbmm7