Valleytronics research advances thanks to bi-layer graphene

Aug 31, 2016

Researchers from Penn State University demonstrated a new device, based on bi-layer graphene, that provides an experimental proof of the ability to control electron-flow by the valley degree of freedom. Valleytronics is a new field of science that aims to create devices that use electron's valley degree of freedom (in a somewhat similar way to Spintronics that aims to do the same with electron spin).

Bi-layer graphene based valleytronics experiment (Penn State)

The device is built from bi-layer graphene. The researchers added an electric field perpendicular to the plane opens a bandgap in the bi-layer graphene, which then enables them to build valleytronics valves in a physical gap present in the device.

Graphene quantum dots and TiO2 exhibit fascinating light harvesting capabilities

Jul 20, 2016

Researchers at Australia's Griffith University have discovered a fascinating mechanism, that may allow the design of a new class of composite materials for light harvesting and optoelectronics. The team has found a quantum-confined bandgap narrowing mechanism, where UV absorption of the graphene quantum dots and TiO2 nanoparticles can easily be extended into the visible light range.

According to the scientists, real life application of this would be high efficiency paintable solar cells and water purification using sun light. In addition, the team states that "this mechanism can be extremely significant for light harvesting. What's more important is we've come up with an easy way to achieve that, to make a UV absorbing material to become a visible light absorber by narrowing the bandgap."

NRL designs low-defect method to nitrogen dope graphene resulting in tunable bandstructure

Jun 07, 2016

A team of scientists at the U.S. Naval Research Laboratory (NRL) has demonstrated hyperthermal ion implantation (HyTII) as an effective means of doping graphene with nitrogen atoms. The result is a low-defect film with a tunable bandstructure that could be useful in a variety of device platforms and applications.

NRL nitrogen-dope graphene image

According to the research, the HyTII method delivers a high degree of control including doping concentration and, for the first time, demonstrates depth control of implantation by doping a single monolayer of graphene in a bilayer graphene stack. This further demonstrates that the resulting films have high-quality electronic transport properties that can be described solely by changes in bandstructure rather than the defect-dominated behavior of graphene films doped or functionalized using other methods.

A novel approach to interconnecting GNRs could lead to high-performance graphene-based electronics

Jan 14, 2016

An international team of researchers at Tohoku University in Japan has demonstrated the ability to interconnect graphene nanoribbons (GNRs) end to end, using molecular assembly that forms elbow structures (interconnection points). This development may provide the key to unlocking GNRs’ potential in high-performance and low-power-consumption electronics.

GNRs are interesting as their width determines their electronic properties; Narrow ones are semiconductors, while wider ones act as conductors, which basically  provides a simple way to engineer a band gap into graphene for use in electronics.

Manipulating graphene's wrinkles could lead to graphene semiconductors

Oct 26, 2015

Researchers at Japan's RIKEN have discovered that wrinkles in graphene can restrict the motion of electrons to one dimension, forming a junction-like structure that changes from zero-gap conductor to semiconductor back to zero-gap conductor. Moreover, they have used the tip of a scanning tunneling microscope to manipulate the formation of wrinkles, opening the way to the construction of graphene semiconductors by manipulating the carbon structure itself in a form of "graphene engineering."

The scientists were able to image the tiny wrinkles using scanning tunneling microscopy, and discovered that there were band gap openings within them, indicating that the wrinkles could act as semiconductors. Two possibilities were Initially considered for the emergence of this band gap. One is that the mechanical strain could cause a magnetic phenomenon, but the scientists ruled this out, and concluded that the phenomenon was caused by the confinement of electrons in a single dimension due to "quantum confinement."