Fig. 1: Concepts of a Yagi-Uda antenna and inelastic electron tunneling.

a SEM micrograph of a Yagi-Uda antenna containing reflector, feed element with kinked connectors and three directors on a glass substrate. b Zoom into the feed element highlighting the asymmetrically positioned particle creating a tunnel gap toward the top antenna arm. c Modeled emission characteristics of a Yagi-Uda antenna in the xz plane (for a homogeneous surrounding). The reflector and director elements lead to a highly unidirectional emission by generating constructive interference in the forward and destructive interference in the backward direction. The intensities in forward and backward direction can be used to define a forward-to-backward (FB) ratio and the antenna gain, see inset. d Schematics of the IET process.