According to the report of the Physicist Organization Network on June 4, researchers at the Center for Nanophysics and Advanced Materials at the University of Maryland developed a new type of thermal electron bolometer that can be widely used in biochemical weapons. Distance detection, airport security scanners and other security imaging technology areas, and promote research on the structure of the universe. The relevant research report was published in the "Nature Nanotechnology" magazine published on June 3.
Scientists developed the bolometer using double-layer graphene. Graphene has a completely zero-energy bandgap, so it can absorb any form of energy photons, especially low energy photons such as terahertz or infrared and submillimeter waves. The so-called photonic band gap means that waves of a certain frequency range cannot propagate in this periodic structure, that is, the structure itself has a "band gap." The photonic bandgap structure can make certain waveband electromagnetic waves completely unable to propagate in it, thus forming a bandgap on the frequency spectrum.
The other characteristic of graphene also makes it very suitable as a photon absorber: the electrons that absorb energy can still maintain their own high efficiency, and will not lose energy because of the vibration of the material atoms. At the same time, this characteristic also makes graphene have very low resistance. The researchers designed a thermal electron bolometer based on these two characteristics of graphene. It can work by measuring the change in resistance caused by electrons heating themselves after absorbing light.
In general, the resistance of graphene is hardly affected by temperature, and it is not suitable for bolometers. Therefore, the researchers used a special technique: When the double-layer graphene is exposed to an electric field, it has a moderate-sized band gap, which can not only connect the resistance and temperature, but also maintain its ability to absorb low-energy infrared photons. .
The researchers found that with a temperature of 5 degrees Kelvin, the new bolometer can achieve the same sensitivity as existing bolometers, but the speed can be increased by more than 1,000 times. They speculate that they can surpass all current detection technologies at lower temperatures.
The new device is particularly promising as a fast, sensitive, low-noise submillimeter wave detector. Submillimeter-wave photons are emitted by relatively cool interstellar molecules and are therefore difficult to detect. By observing these interstellar molecular clouds, astronomers can study the early stages of the formation of stars and galaxies. Sensitive submillimeter wave detectors can help build new observatories and determine the red shift and quality of very distant young galaxies, thus advancing research on the development of dark energy and the structure of the universe.
Although some challenges still exist, such as double-layer graphene can only absorb a small part of the incident light, this makes the new bolometers have higher resistance than similar devices using other materials, so it is difficult to be normal at high frequencies. Work, but researchers say they are working hard to improve their designs to overcome these difficulties, and they also have great confidence in the bright future of graphene as a photoelectric detection material. (Zhang Hao)
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