Pulsed and Coherent Electron Emissions from Tungsten Nanotips

Pulsed coherent electron sources are highly demanded for the development of time-resolved electron diffraction and imaging techniques. Here, we report quantitative measurements of the pulse width and the spatial coherence for electrons emitted from tungsten nanotips. The pulse width of 340 eV electrons from a homemade needle is determined to be about 7.3 picoseconds using a pump (femtosecond optical pulse) -probe (electron pulse) method. DC-field emission from a commercial sharp needle tip achieves a transverse coherence length about 70 nanometers. These results highlight the potential of tip-based electron sources for ultrafast electron diffraction and imaging application.