A nanometer-sized few femtosecond electron source at high repetition rates

This paper describes and demonstrates a novel approach towards realizing a point-like ultrafast electron source. By illuminating ultrasharp gold tips with 7-fs pulses from an 80 MHz Ti:sapphire oscillator, an intense flux of up to 107 electrons per second is induced. Due to the local field enhancement this emission is strongly localized at the apex of the metallic tip with a radius of curvature of only few tens of nanometers. The multiphoton character of the electron generation in the absence of a tip bias voltage is demonstrated. The results of first imaging experiments using this novel electron source will be presented, demonstrating near-field imaging of local electric fields with about 20 nm spatial resolution.