The silicon-based transistor generally depends on the charge of electrons. It turns the device ON or OFF. However, various scientists are attempting to develop a new approach to manipulating electrons based on other variables. It is called degrees of freedom.
The charge is the first degree of autonomy, electron spin is another, and the valley state of electrons is the third one. The ability to develop spin-based transistors is known as spintronics. The valley state of electrons depends on their energy in relation to their momentum.
Scientists from Penn State University have developed a device made of bilayer graphene. It has the ability to control the momentum of electrons. It requires a lower amount of energy and generates less heat than standard CMOS transistors.
Jun Zhu, associate professor of physics at Penn State, suggests: “Think of electronics as cars and the valley as blue and red colors, just like a way to differentiate them. Inside a sheet of bilayer graphene, electrons will normally occupy both red and blue valley states and travel in all directions.”
This new system puts a pair of gates above and below the graphene sheet. After that, an electric field was added at a right angle to the plane.
The positive voltage is applied to one side, whereas a negative voltage is applied to the other side. Thus, it creates a band gap in bilayer graphene. Between the two sides, there is a physical gap of 70 nanometers.
A one-dimensional metallic state or wires permeate this physical gap. Those are a color-coded pathway for electrons. Red colored electrons travel through one side, whereas blue colored electrons pass through the opposite side.
In theory, colored electrons could travel easily along the wires over long distances with minimal resistance. This small resistance means power consumption is inferior in electronic devices and less heat is generated.
This experiment demonstrates that such a state can be created within the interior of insulating bilayer graphene sheets. This is possible by using just a few gates.
Now, scientists are conducting various experiments to determine where resistance might originate. They are also trying to develop valves that manage the flow of electrons based on the color of electrons. This new concept is known as valleytronics.
Chad Eichfeld, Nanolithography Engineer, said, “The alignment of the top and bottom gates was crucial and not a trivial challenge. The state of the art electron beam lithography capabilities allowed Jing to create this novel device with nanoscale features.”
