Will Stanene become graphene's rival in terms of electrical conductivity?

A collaboration between researchers at Stanford University and four universities in China yielded a material made of a single layer of tin atoms, that could be the world's first material to conduct electricity with 100% efficiency at room temperature. The material, called Stanene, is believed to be a rival to graphene and other two-dimensional materials like phosphorene, silicene or germanene, because it is believed to be so conductive as to allow flow of electricity without any heat loss.

The scientists created the mesh by vaporising tin in a vacuum and allowing the atoms to collect on a supporting surface of bismuth telluride. As a result, a two-dimensional honeycomb structure of tin atoms was made. Alas, the substrate and stanene interacted to disrupt the conditions that would have created the perfect conductor - so the team plans to use larger amounts of tin and an inert substrate to rule out interaction. In fact, not all researchers are even sure that the structure created at Stanford is indeed stanene. Direct measurements of the crystal arrangements only can confirm this but that will call for larger amounts of the material.

Wrapping graphene around wires may boost chip speeds

A series of Stanford-led experiments demonstrate that graphene may be able to replace tantalum nitride as a sheathing material for chip wires, to help electrons move through the copper wires more quickly. The scientists say that using graphene to wrap wires could allow transistors to exchange data faster than is currently possible and the advantages of using graphene could become even greater in the future, as transistors continue to reduce in size.

The protective layer isolates the copper from the silicon on the chip and also serves to conduct electricity. Its significance is great since it keeps the copper from migrating into the silicon transistors and rendering them non-functional. Graphene has several advantages for this kind of application: the scientists could use a layer eight times thinner than the industry-standard and get the same effect, and the graphene also acts as a barrier to prevent copper atoms from infiltrating the silicon. The Stanford experiment showed that graphene could perform this isolating role while also serving as an auxiliary conductor of electrons. Its structure allows electrons to move from one carbon atom to another, down the wire, while effectively containing the copper atoms within the copper wire. 

Graphene as a substrate for assembling small organic molecules and heterostructures

Researchers at the University of Stanford in the US, the Ulsan National Institute of Science and Technology (UNIST) in South Korea and Queen’s University in the UK showed that graphene is an excellent substrate for assembling small organic molecules and that such heterostructures might be used in applications like high-performance detectors, solar cells and flexible transistors.

The researchers began by preparing suspended graphene films. They then evaporated C60 molecules onto the films to form thin-film crystals.They then made the resulting structures up into vertical transistors doped with n-type semiconducting materials and found that these devices have current on/off ratios of more than 3 x 103. Various transmission electron microscopy techniques, including selective area electron diffraction, atomic resolution TEM imaging, and van der Waals-based first principles computational methods allowed the researchers to study the structure and grain size of the crystals in detail and carefully look at the graphene-C60 interface in particular. They also noticed that the C60 films lay uniformly on the graphene substrate and that the individual molecules can assume several different molecular orientations.

Spiraling laser pulses find graphene's on/off switch

Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the Stanford Institute for Materials and Energy Sciences (SIMES) collaborated to study the effects of spiraling pulses of laser light on graphene. They discovered that such spiraling laser pulses can theoretically change the electronic properties of graphene, switching it back and forth from a metallic state (where electrons flow freely), to an insulating state.

Such ability could mean that it is possible to use light to encode information in a computer memory, for instance. The study, while theoretical, attempted to work in as close-to-real experimental conditions as possible, right down to the shape of the laser pulses. The team found that the laser's interaction with graphene yielded surprising results, producing a band gap and also inducing a quantum state in which the graphene has a so-called “Chern number” of either one or zero, which results from a phenomenon known as Berry curvature and offers another on/off state that scientists might be able to exploit.