How the atomic lattice and defects affects charge transport in anisotropic surfaces

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In this project will will utilize the molecular nanoprobe (MONA) method we recently developed to investigate how charge transport is affected by the atomic lattice of single-crystalline surfaces and of metallic and non-metallic adsorbates. In the MONA method charge carriers are injected from an STM tip into the surface and detected by means of a reversible, electron-induced switching prozess of a detector molecule which is placed a few nanometer from the STM tip. Through numerous repetitions of this injection-detection process and statistical data analysis we are able to better understand local transport properties. For example, we successfully demonstrated on a 10 nm length scale that quantum-mechanical interference effects determine the transport of hot electrons in the Ag(111) surface which exhibits a characteristic, though highly isotropic surface state. Here we propose experiments on highly anisotropic surfaces. Since these surfaces host highly anisotropic constant-energy contours of the charge density we expect a striking direction-dependence of the charge transport. For example, focussing of the charge transport might be observed due to the periodic potential of the atomic lattice or due to the nesting of the corresponding constant-energy contours. The MONA technique will enable us to detect this focussing in real space on a length scale comparable to the wavelength of the contributing electronic states. Preliminary studies performed on Pd(110) indeed reveal a striking directional dependence of the molecular switching rate, thereby confirming our expectation.