Hungarian researchers unveiled hot electrons with the help of lasers

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Researchers of the ELI-ALPS Laser Research Institute, the ELKH Wigner Research Centre for Physics (Wigner RCP), the University of Szeged (SZTE) and the ELKH Centre for Energy Research (EK-CER) have made significant progress in examining the properties of so-called hot electrons in metals. The results of the research can be used with important applications such as the development of solar cells and nanoscale circuits, or improvement of the sensitivity of various sensor types. A study presenting the results was published in the prestigious journal Nature Communications.

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Generation of hot electrons with laser light in a nanometric metal layer (Image credit: B. Major)

By illuminating metals with light high-energy electrons can be generated. These are called hot electrons. Due to their excess energy these electrons can be exploited in various fields, such as catalyzing chemical reactions, making solar cells more efficient, increasing sensitivity of sensors and even developing nanoscale circuitry.

However, it is very difficult to probe these hot electrons experimentally, since such electrons remain in the metal even after the arrival of the light beam. Nevertheless, for future applications it is important to know how much extra energy they have and where they are located within the material.

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Researchers of ELI-ALPS and Wigner RCP conducting a laser experiment

The team has developed a radically new and more sensitive approach for studying hot electrons. In their experiments they investigated the reflection properties of light emitted onto the sample with a nanometer thin gold layer while hot electrons were created in it using laser light. By analyzing the changes in the reflection properties they found that these electrons were concentrated very close to the surface in a depth of only about 4 nanometers. The analysis of the excess energy of these electrons also provided information on the steps the hot electrons take upon their generation. These results will be of immense importance to the development of electron-based devices or solar cells.