An international research team has created a novel surface coating technology that can greatly boost electron emission in materials. Their discovery is likely to boost the manufacture of high-efficiency electron sources, as well as improve the performance of electron microscopes, electron beam lithography systems, and synchrotron radiation facilities.
Image Credit: Tohoku University.
Free electrons are not connected to an atom or molecule and can move freely within a substance. They are essential in a wide range of applications, including microscopes, photoreactors, and accelerators.
The work function is one feature that measures the performance of free electrons: the minimum energy necessary for electrons to escape from a material’s surface into a vacuum. Materials with a low work function consume less energy to remove electrons and liberate them, whereas materials with a high work function require more energy to remove electrons.
Lower work functions are essential in improving electron source performance and contributing to developing innovative materials and technologies with practical applications in disciplines like accelerator science, electron microscopy, and semiconductor manufacturing.
Because of its great stability and longevity, hexaboride lanthanum (LaB6) is now commonly used for electron sources. To increase the efficiency of LaB6, the researchers used hexagonal boron nitride (hBN), a versatile chemical molecule that is thermally stable, has a high melting point, and is useful in adverse environments.
We discovered that coating LaB6 with hBN lowered the work function from 2.2 eV to 1.9 eV and increased electron emission.
Shuichi Ogawa, Study Co-Author and Associate Professor, Nihon University
Shuichi Ogawa was formerly associated with Tohoku University’s Institute of Multidisciplinary Research for Advanced Materials.
Photoemission electron microscopy and thermionic emission electron microscopy accomplished by the team ascertained the lower work function compared to non-coated and graphene-coated regions.
Ogawa and his co-workers intend to improve the coating technique in the future.
We still need to develop a technique for coating hBN onto LaB6’s non-oxidized surface, as well as a way to coat LaB6 electron sources with a pointed triangular shape.
Shuichi Ogawa, Study Co-Author and Associate Professor, Nihon University
Journal Reference:
Yamaguchi, H., et al. (2023). Work function lowering of LaB6 by monolayer hexagonal boron nitride coating for improved photo- and thermionic-cathodes. Applied Physics Letters. doi.org/10.1063/5.0142591.