Ultrafast photo-triggered field emission cathodes using massive, uniform arrays of nano-sharp high-aspect-ratio silicon structures

We report the design, fabrication, and experimental characterization of a novel ultrafast optical field emission cathode comprised of a large and dense array of nano-sharp high-aspect-ratio single-crystal silicon columns (>100,000 tips, 4.6-million tips.cm-2). The cathode emits electrons with as little as 25 nJ and can produce up to 2.54 pC electron bunches per laser pulse when interacting with 35 fs 800 nm laser pulses with a 765 μm by 80 μm elliptical spot size. This is the first report of current measurements from Si tip arrays using photo-field emission; in addition, this is the first demonstration of a photocathode array that, depending on the energy of the laser pulses, can emit in the multi-photon or the tunnelling regime.