A Semiconductor Photocathode with Electrostatically Tunable Electron Affinity Surface

Electrostatically tunable negative electron affinity (NEA) semiconductor photocathode can be a stable alternative to chemically activated NEA surfaces, which are highly sensitive to atmospheric exposure. Here we present a planar silicon-insulator-graphene heterostructure-based Hot-Electron Light-Assisted Cathode (HELAC) [1, 2], that enables reversible, air-stable NEA operation. Unlike conventional cathodes, HELAC offers independent electronic control over emission parameters, eliminating its dependence on surface chemistry. Together with its structural simplicity and scalability, these features establish HELAC as a transformative platform for the development of nextgeneration compact, optically modulated, and highfrequency electron source.