How elementary charges propagate on surfaces or interfaces is of fundamental interest for a myriad of technical applications. Since the building blocks of current electronics products are getting smaller and smaller, the investigation of charge transport on atomic length scales would be highly beneficial. The so-called molecular nanoprobe (MONA) technique, which has recently been developed in our group, uniquely allows for transport studies down to few atom length scales.
In a paper just published in Physical Review Letters we report on the first observation of anisotropic hole transport on the (110) surface of face-centered cubic metal Palladium (Pd). Using a single cis-2-butene molecule as a detector, we investigate the transport of charge carriers that are injected by an STM tip a few nanometers away from the molecule. As shown in the left sketch, we observe strongly ansiotropic charge transport, with a dip along the the atomic rows of Pd(110) and a peak in the transverse direction. Our measurements provide first evidence that the nanometer-scale charge transport properties of metallic surfaces is significantly influenced by scattering events with single atomic rows.