A team of researchers from TU Wien has shed new light on the behavior of electrons fleeing a solid material.<\/p>\n
Their research solves a long-standing mystery in condensed matter physics. When a material is bombarded with electrons, this transfers energy, allowing other electrons within the solid material to escape. <\/p>\n
This secondary electron emission mechanism is leveraged in many technologies today, including photomultiplier tubes, scanning electron microscopes, and cathode ray tubes. However, until now, scientists haven\u2019t been able to predict which specific electrons would escape from a given material.<\/p>\n
The new study reveals the critical role of \u201cdoorway states\u201d, which dictate the electrons that can leave a solid material.<\/p>\n
The electron emission mystery<\/p>\n
Within a solid material, electrons have different energies. If they remain below a specific energy threshold, they cannot escape the material.<\/p>\n
Imagine a frog standing inside a box with a high opening, for instance. For the frog to escape the box, it has to have enough energy to jump, and it has to find the exit. It\u2019s as simple as that. <\/p>\n
Scientists initially believed electrons would follow this same level of simplicity when escaping a material. They assumed there would be a direct relationship between an electron\u2019s energy and its emission \u2013 or escape \u2013 probability. However, experimental observations have repeatedly contradicted this assumption. These discrepancies indicated that electron energy isn\u2019t the only factor driving electron emission. <\/p>\n
\u201cOne might assume that all these electrons, once they have enough energy, simply leave the material,\u201d Prof. Richard Wilhelm, head of the Atomic and Plasma Physics group at TU Wien, explained in a press statement<\/a>. \u201cIf that were true, things would be simple: we would just look at the electrons\u2019 energies inside the material and directly infer which electrons should appear outside. But, as it turns out, that\u2019s not what happens.\u201d<\/p>\n As the study\u2019s first author, Anna Niggas added, theoretical predictions and experimental results have provided more questions than answers. \u201cDifferent materials \u2014 such as graphene structures with different amounts of layers \u2014 can have very similar electron energy levels, yet show completely different behaviors in the emitted electrons,\u201d she explained.<\/p>\n Discovering \u2018doorway states\u2019<\/p>\n