Physicists unlock the mystery of thermionic emissions in graphene
When a metal is heated to a sufficiently high temperature, electrons can be ejected out from the surface in a process known as the thermionic emission, a process that is similar to the evaporation of water molecules from the surface of boiling water.
The thermionic emission of electrons plays an important role in both fundamental physics and digital electronic technology. Historically, the discovery of thermionic emission enables physicists to produce beams of free-flowing electrons in a vacuum. Such electron beams had been used in the hallmark experiments performed by Clinton Davisson and Lester Germer in the 1920s' to illustrate the wave-particle duality of electrons—a bizarre consequence of quantum physics, which marked the dawn of the modern quantum era. Technologically, thermionic emission forms the core of vacuum tube technology—the precursor of modern-day transistor technology—that enabled the development of the first-generation digital computer. Today, thermionic emission remains one of the most important electricity conduction mechanisms that governs the operation of billions of transistors embedded in our modern-day computers and smartphones.
Although thermionic emission in traditional materials, such as copper and silicon, has been well-explained by a theoretical model put forward by British physicist O. W. Richardson in 1901, exactly how thermionic emission takes place in graphene, a one-atom thin nanomaterials with highly unusual physical properties, remains a poorly understood problem.
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