Photocathodes

Photocathodes were at the heart of quantum physics development in the early twentieth century and are still used in high technology devices like night-vision goggles, photomultiplier tubes, and particle accelerators. The simplest form of the photocathode is a metallic surface, negatively biased, from which electrons are extracted by energetic photons. After a brief description of the photocathode preparation, this chapter will present the latest developments and limitations of metallic and semiconductor photocathodes.