Scientists excited plasmons on the surface of graphene

According to the report of the Physicist Organization Network on June 20, scientists at the University of California, San Diego used infrared beams to excite electron waves along the surface of graphene and proved that they can control these so-called plasmons through simple circuits. The length and height of the oscillating wave. The relevant research report was published on the June 21 issue of Nature magazine.

This is the first time that a plasmon has been observed on graphene. It is also an important step in information processing using a plasmon in a space where light cannot be used. Just as light can carry complex signals through optical fibers, plasmons can also be used to transmit information. However, plasmons can only carry information in a tighter space. Dimitry Basov, professor of physics at the university, said: “Everyone doubts that the plasmons will appear, but seeing it is true. The images we take can prove their spread and their control. ”

In order to make this device, researchers peeled off graphene from graphite and placed it on a silicon chip to rub it. An infrared laser was then irradiated on the surface of the graphene to excite the plasmons and these waves were measured using an ultra-sensitive atomic force microscope cantilever.

Although the emitted waves are almost impossible to measure, when they reach the edge of the graphene, waves like water ripples can be reflected. The return from the edge will increase or cancel the subsequent waves, creating a unique interference pattern that reveals the wavelength and amplitude of these waves. In addition, scientists can change the interference pattern by controlling the circuit formed by the electrode attached to the surface of graphene and the pure silicon layer under the chip.

Researchers say that since the wavelength of light is hundreds of nanometers, it is impossible to limit light to the nanometer level. However, the use of light can excite surface plasmons with a length range of about 100 nanometers, which can traverse from one side of the chip to the other at an extremely high speed. Scientists say that this is one of the shortest measured plasmon wavelengths, but this wave can travel as much as they do in metals such as gold. Unlike metal-based plasmons, graphene plasmons can be adjusted as needed.

By monitoring graphene plasmons, researchers can understand what role electrons play in this new form of carbon and how their basic interactions will govern their properties. Basov stressed: “Graphene optoelectronics and information processing are very promising, and we hope that this study can provide help for the development of related technologies in the future.” (Zhang Hao)

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