New Surface Coating Increases Electron Emission Sevenfold

New Surface Coating Technology Increases Electron Emission Sevenfold An international research group has developed a new surface coating technology capable of significantly increasing electron emission from materials. The invention is expected to improve the production of high-efficiency electron sources and enhance performance in electron microscopes, electron beam lithography systems, and synchrotron radiation facilities. The research was published on 3 April 2023 in Applied Physics Letters. Free electrons are electrons not bound to a specific atom or molecule, circulating freely within a material. They play a vital role in a wide range of applications, from photoreactors and microscopes to accelerators. A key property measuring the performance of free electrons is work function: the minimum energy required for electrons to escape from a material surface into vacuum. Materials with low work function require less energy to remove electrons and allow them to move freely; whereas materials with high work function require more energy to remove electrons. A lower work function is critical for improving the performance of electron sources and could have practical applications in various fields such as electron microscopy, accelerator science, and semiconductor manufacturing by contributing to the development of advanced materials and technologies. Currently, lanthanum hexaboride (LaB6) is widely used for electron sources due to its high stability and durability. The research group turned to hexagonal boron nitride (hBN), a versatile chemical compound that is thermally stable, has a high melting point, and is highly useful in demanding environments, to enhance LaB6 efficiency. Shuichi Ogawa, co-author of the study and associate professor at Nihon University (formerly at Tohoku University Multidisciplinary Research Institute for Advanced Materials), stated: "We discovered that coating LaB6 with hBN reduced the work function from 2.2 eV to 1.9 eV and increased electron emission." Photoemission electron microscopy and thermionic emission electron microscopy performed by the research team confirmed the lower work function compared to uncoated and graphene-coated regions. Ogawa and his colleagues aim to further develop the coating technique in the future. "We need to develop a technique for coating hBN onto the unoxidized surface of LaB6, as well as a method for coating LaB6 electron sources in a sharp triangular shape." Academic Reference: Hisato Yamaguchi et al, Work function lowering of LaB6 by monolayer hexagonal boron nitride coating for improved photo-and thermionic-cathodes, Applied Physics Letters (2023). DOI: 10.1063/5.0142591 Source