Articles you may be interested inPhotoassisted electron emission from metal-oxide-semiconductor cathodes based on nanocrystalline silicon Though present photoemitting cathodes have attained quantum yields, lifetimes, dark currents, and response times as required by high-luminosity accelerators, their use is hampered by their high reactivity to residual gases even in ultra-high-vacuum conditions. Ultrathin ͑20-200 nm͒ films of nanostructured sp 2 carbon, directly grown on photocathodes by supersonic cluster-beam deposition, besides providing a strongly bound, inert protective coating, are shown to maintain the photoemission efficiency of clean metallic substrate cathodes. Moreover, nanostructured carbon coating is shown to induce strong nonlinearities in photoemission at high intensities, which can be explained as due to the Auger effect.