A groundbreaking surface coating technology has been successfully developed by an international research group. This innovative advancement has the remarkable ability to significantly enhance electron emission in various materials. The implications of this breakthrough are expected to revolutionize the production of high-efficiency electron sources, leading to substantial improvements in electron microscopes, electron beam lithography systems, and synchrotron radiation facilities. These exciting findings were recently published in the prestigious journal Applied Physics Letters on April 3, 2023.
Free electrons, which are unbound to specific atoms or molecules, are crucial components in a wide array of applications ranging from photoreactors and microscopes to accelerators. Evaluating the performance of free electrons involves considering their work function, which represents the minimum energy required for electrons to escape from the surface of a material into a vacuum. Materials with a low work function necessitate less energy to liberate electrons, allowing them to move freely. On the other hand, materials with a high work function demand more energy to release electrons.
Achieving a lower work function is of utmost importance in enhancing the performance of electron sources and advancing the development of cutting-edge materials and technologies. These advancements hold tremendous practical implications in various fields, including electron microscopy, accelerator science, and semiconductor manufacturing.
The utilization of hexaboride lanthanum (LaB6) has become prevalent in electron sources due to its remarkable stability and durability. However, in a quest for enhanced efficiency, the research group turned their attention to hexagonal boron nitride (hBN), a versatile chemical compound known for its thermal stability, high melting point, and suitability for challenging environments.
“We made an intriguing discovery that applying a coating of hBN onto LaB6 resulted in a reduction of the work function from 2.2 eV to 1.9 eV, consequently amplifying electron emission,” revealed Shuichi Ogawa, co-author of the study and current associate professor at Nihon University (previously affiliated with Tohoku University’s Institute of Multidisciplinary Research for Advanced Materials).
The research group employed photoemission electron microscopy and thermionic emission electron microscopy to validate the lower work function observed in the coated regions compared to non-coated and graphene-coated areas.
Looking towards the future, Ogawa and his colleagues aim to refine the coating technique further. “Our next focus is to develop a method for coating hBN onto the non-oxidized surface of LaB6, as well as devising a means to coat LaB6 electron sources with a pointed triangular shape.”
Source: Tohoku University