Research in Field Emitter Arrays
Required electric field to generated field electron emission is extremely high, 1-5 GV/m, but can be achieved by using extremely sharp nanotips. When one of the electrode of a capacitor is replaced with such a nanotip with the tip apex radius of curvature in nanometers range, the tip apex field can be several orders of magnitude higher than the uniform field defined by the macroscopic separation between the capacitor electrode.
With the double-gate field emitter arrays, one can colliamte the individual beamlets from the emitter arrays by applying a potential to on-chip beam collimation gate electrode. Combined with the high current, high current density, and laser-induced field emission, we aim at realizing a new cathode with extremely brightness.
 S. Tsujino, F. le Pimpec, J. Raabe, M. Buess, M. Dehler, E. Kirk, J. Gobrecht, and A. Wrulich, Static and optical field enhancement in metallic nanotips studied by two-photon photoemission microscopy and spectroscopy excited by picosecond laser pulses, Appl. Phys. Lett. 94, 093508 (2009); Selected for the March 16, 2009 issue of Virtual Journal of Nanoscale Science & Technology; Selected for April 2009 issue (Volume 8, Issue 4) of Virtual Journal of Ultrafast Science.
 S. Tsujino, P. Beaud, E. Kirk, T. Vogel, H. Sehr, J. Gobrecht, and A. Wrulich Ultrafast electron emission from metallic nanotip arrays induced by near infrared femtosecond laser pulses, Appl. Phys. Lett. 92, 193501 (2008); Selected in Virtual Journal of Ultrafast Science -- June 2008, Volume 7, Issue 6.
 A. Mustonen, P. Beaud, E. Kirk, T. Feurer, and S. Tsujino, Five picocoulomb electron bunch generation by ultrafast laser-induced field emission from metallic nano-tip arrays, Appl. Phys. Lett. 99, 103504 (2011); Selected for September 19, 2011 issue (Volume 24, Issue 12) of Virtual Journal of Nanoscale Science & Technology; Selected for October 2011 issue (Volume 10, Issue 10) of Virtual Journal of Ultrafast Science; highlighted in Nature Photonics, 5, 644-645 (November 2011).
 P. Helfenstein, E. Kirk, K. Jefimovs, T. Vogel, C. Escher, H.-W. Fink, and S. Tsujino, Highly collimated electron beams from double-gate field emitter arrays with large collimation gate apertures, Appl. Phys. Lett. 98, 061502 (2011).