A novel fiber tip based electron source

In this paper we report on the first experimental characterization of a fiber tip-based electron source where the electron emission is triggered by both, electric field and optical excitation. Our approach consists of coating a commercial 100 nm apex size NSOM multi-mode fiber tip with a 10 nm thick tungsten layer, which is back-illuminated in the presence of an extraction electric field. The measurements show a clear enhancement of the emission by the incident light, but the emission response time is slower than the optical trigger time, suggesting that thermal effects are predominant. This hypothesis is backed up by the temporal response measurements of the tip temperature.