Figure 7
Electron emission patterns from the tungsten tip.
(a) Electron emission patterns without laser illumination, measured with a tip voltage Vtip of −2800 V. The inset of (a) shows the front view of the atomic structure of the tip apex based on a ball model, in which green areas with white edges indicate the emission sites. (b) A laser-induced field emission pattern. The tip voltage Vtip was −1900 V and the laser peak intensity was 1 × 1012 W/cm2. Red circles indicate positions of the pinhole during measurements of the energy spectra.
