Nanostructured silicon photo-cathodes for x-ray generation

We report the fabrication and characterization of ultrafast laser triggered nanostructured silicon photo-cathodes for x-ray generation via inverse Compton scattering. A highly uniform array of ~2200 silicon pillars with 5 μm array pitch, where each pillar is capped by a nanosharp tip, shows stable current emission using 35 fs, 800 nm laser pulses. The cathodes can emit at 3.6 nA average current over 8-million 1.2 pC electron bunches when excited with 9.5 μJ laser pulses with no degradation of the emission characteristic of the cathode, showing that silicon-based photon-triggered cathodes processed with standard CMOS processes and operated at high vacuum can function for extended periods without performance degradation.