Scientists developed an ultrathin film of cesium antimonide that can be used as a highly efficient photocathode. The study was published in the journal Physical Review Letters. Scientists describes their approach to create the photocathode and how it performed when compared to conventional photocathodes.
A photocathode is a device that converts photons into electrons via the photoelectric effect. Such devices are made of a material that releases an electron when struck by a photon. They can be gathered into a beam for use in applications such as free-electron lasers and electron diffraction, when large numbers of electrons are produced. Scientists have continued to search for ways to increase the efficiency of such devices, as the technology has matured.
Scientists developed a new kind of photocathode using antimony and cesium.
Scientists applied a form of epitaxy, antimony and cesium that had undergone an extremely thorough filtering process and sublimated inside of a vacuum chamber where they condensed onto a silicon carbide substrate. The action occurred one atomic layer at a time with the atomic structure of the material that was created in the same orientation as the substrate, ensuring that it was free of defects. The ultrathin films that resulted were just 4 nm thick and could be used as a photocathode.
The team then set about analyzing the film to ensure that it was defect-free and that the layers had been deposited on the substrate in the manner intended. Scientists began testing the film to see how it compared with conventional films.
Scientists found that when converting green light into electrons. The efficiency of their photocathode was greater than 2% and its process was as short as 10 fs. It is significantly faster than conventional photocathodes. They conclude that similar photocathodes could be used to create new devices with significant brightness enhancements.