In a cooperative development between the Fritz-Haber Institute (Berlin) and the University of Colorado (Boulder), researchers have demonstrated an electron source whose temporal resolution lies below 10 fs. In their (electron) lens-less system, they couple brief laser pulses to a grating on the side of a metallic cone, generating surface plasmon polaritons which focus the pulse energy to the conical tip, whereupon electron emission occurs from the tip alone.
In addition to various measurements of the emission itself, the authors demonstrate scans over an isolated InP nanowire, in which the P/N junction is clearly visible while the scanning tip is 3 µm distant.
Reference: M Müller, et al., “A nanofocused plasmon-driven sub-10 femtosecond electron point source”, arXiv:1512.07037.