Behavior of photocathodes on superficial modification by electrical breakdown

In this work we present the experimental study and a theoretical approach of the photoemission of rough and smooth photocathodes. The cathode bulk was made of pure yttrium while its surface was morphologically modified. The cathode surface was irradiated by a KrF excimer at normal incidence with the anode-cathode distance set to 5mm. The measurements were performed after electric breakdowns between anode and cathode, induced under high laser energy and high accelerating voltage. This operation was made in order to increase the surface roughness. For the rough cathode the maximum output current was 10.5 A, reached at 25 kV and 12 mJ, with a maximum quantum efficiency value of 1.3×10-4. Instead, under the same experimental conditions the smooth cathode provided an output current of 8.4 A with a maximum quantum efficiency value of 7.0×10-5. We can conclude that in this process the plasma production and the Schottky effect play a fundamental role.