A device made of double-layer graphene, a thin layer of carbon atoms arranged in a hexagonal pattern, provides experimental evidence of electron momentum control and provides a method that is more conductive than standard CMOS transistors Less energy and way to emit fewer thermal electronics. This is a step toward a new field of physics called valley electronics.
"Today's silicon-based transistor devices rely on electronic charges to switch devices, but many are looking for new ways to manipulate electrons based on other variables called degrees of freedom," said Jun Zhu, the research leader He is an assistant professor of physics at Penn State University. Charge is one of the degrees of freedom.Electrospin is another degree of freedom, and the ability to spin-spin-make transistors called spintronics is still under development. The third degree of freedom for electrons is the electron valley State, based on the energy associated with their momentum. "
Zhu says that you can think of electronics as a car, using the color of the valley as a red or blue car, etc., as a way of differentiating them. In a thin layer of double-graphene, electrons usually occupy both red and blue valleys and move in all directions. The device, researched by her PhD student Jing Li, allows the red car to move in one direction and the blue car in the opposite direction.
"Jing's system has a pair of gates above and below the double-layered graphene sheet, and then he applies an electric field perpendicular to the plane," Zhu said.
"By applying a positive voltage on one side and a negative voltage on the other side, a bandgap is opened in the two-layer graphene, which is usually absent and in the middle of the two sides we reserve A physical gap of about 70 nanometers, "Li explains.
This is a scanning electron microscope image of the device used in this experiment. Layers of graphene and hexagonal boron nitride are stacked together and the device is then electron beam lithographed. The purple layer is a double graphene sheet. The bottom pair of separate gate pairs (black squares) is made of multiple layers of graphene. The top separate gate pair (gold square) is made of gold. This one-dimensional line exists within the gap formed by the separate gates.
Within this gap there is a one-dimensional metallic state, or a metal line, which is a color coded electronic highway. On these roads, the red car moves in one direction while the blue car moves in the opposite direction. In theory, colored electrons can travel a very long distance along the wire with little resistance, almost unimpeded. A small resistance means that the electronics consume less power and generate less heat. Power consumption and thermal management are all challenges in today's miniaturized devices.
"Our experiments show that wire can be made," Li said. "Although we are still a long way from being practical."
Zhu added: "It is not unusual for these states to be created inside insulated double-layer graphene sheets using only a few gates. They are not yet completely impedanceless, and we are doing more experiments to see how the impedance may come from We are also trying to create a valve that controls the flow of electrons based on the color of the electrons, a new electronic concept called Valley Electronics. "
Li worked closely with technicians at Penn State's nanofabrication lab to turn the theoretical framework into a working device.
"The alignment of the top and bottom gates is critical and an extraordinary challenge." The advanced electron beam lithography capabilities at Penn State University's nanolatritors enabled Jing to create this new device with nano-capabilities , "Says nanolithography engineer Chad Eichfeld.
Their paper, entitled "Gated Topology Conductive Passages for Bilayer Graphene," was published online August 29 in Nature Nanotechnology magazine. Other authors include Ke Wang of China University of Science and Technology, Yafei Ren and their mentor Zenhua Qiao, who conducted numerical studies to simulate the behavior of metal wires. High-quality hexagonal boron nitride crystals used in this experiment were from Kenji Watanabe and Takashi Taniguchi at the National Institute of Materials Science. Two undergraduate students, Kenton McFaul and Zachary Zern, also contributed to the study.
Funding for the study was provided by the U.S. Naval Research Office, the National Science Foundation, and funding agencies in China and Japan. Kenton McFaul, a visiting student at the Grove City College, is funded by a University Research Internship Program licensed by the National Science Foundation (NSF) and the National Institute of Basic Nanotechnology (NNIN). Jun Zhu is a member of the 2D Layered Materials Center at Penn State University Institute of Materials.
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