The Weizmann Institute of Science today announced that a research group headed by Dr. Ernesto Joselevich has developed a new approach to create patterns of carbon nanotubes by formation along atomic steps on sapphire surfaces. Carbon nanotubes are excellent candidates for the production of nanoelectronic circuits, but their assembly into ordered arrays remains a major obstacle toward this application.
The team was initially researching in a different direction: they were trying to give carbon nanotubes (structures reminiscent of rolled-up sheets of graphite) a preferred orientation on a wafer by applying an electrical field as the tubes were being formed. This works very well with silicon dioxide wafers. On a sapphire support (sapphire is a form of aluminum oxide), on the other hand, it didnt work: the nanotubes were beautifully arranged in parallel, but with an orientation that was completely independent of the electrical field – even when no field was applied at all.
Closer examination of the sapphire surface solved the mystery: commercial sapphire wafers are generally not cut exactly along the plane of the crystal. Their surface is thus not completely smooth; instead, it has parallel steps – of atomic dimensions – between the different planes of the crystal. The nanotubes wind up lying along these steps. The researchers explain it like this: the nanotubes form from a catalyst of iron nanoparticles and are attracted to a local field created by the steps. It is clear that these iron particles dont like "climbing stairs;" instead, they "glide" along the inner edge of the step, as though on a track. Thus they remain continuously in contact with two surfaces, rather than just one, which seems to stabilize the catalyst. Just as an airplane leaves behind a condensation trail, the iron particles leave the newly formed nanotubes lying along their "tracks." The nanotubes even follow kinks in the steps, which are caused by defects in the crystal. This results in either straight or zigzag-shaped tubes, which are expected to have particularly interesting electronic properties.
Yivsam Azgad | EurekAlert!
Scientists propose synestia, a new type of planetary object
23.05.2017 | University of California - Davis
Turmoil in sluggish electrons’ existence
23.05.2017 | Max-Planck-Institut für Quantenoptik
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering