Abstract
Miniaturization of electronic circuits into the single-atom level requires novel approaches to characterize transport properties. Due to its unrivaled precision, scanning probe microscopy is regarded as the method of choice for local characterization of atoms and single molecules supported on surfaces. Here we investigate electronic transport along the anisotropic germanium (001) surface with the use of two-probe scanning tunneling spectroscopy and first-principles transport calculations. We introduce a method for the determination of the transconductance in our two-probe experimental setup and demonstrate how it captures energy-resolved information about electronic transport through the unoccupied surface states. The sequential opening of two transport channels within the quasi-one-dimensional Ge dimer rows in the surface gives rise to two distinct resonances in the transconductance spectroscopic signal, consistent with phase-coherence lengths of up to 50 nm and anisotropic electron propagation. Our work paves the way for the electronic transport characterization of quantum circuits engineered on surfaces.
Highlights
Miniaturization of electronic circuits into the single-atom level requires novel approaches to characterize transport properties
The precision reached in approaching the scanning tunneling microscope (STM) tip apex toward the surface permits for a controlled electronic contact with a single surface atom or molecule[7,8]
Such vertical contacts formed by STM can be used to study electronic transport through adsorbates with atomic-scale lateral resolution[9,10,11,12,13,14]
Summary
Miniaturization of electronic circuits into the single-atom level requires novel approaches to characterize transport properties. As our transconductance results are consistent with the picture that electrons propagate elastically along the rows, in order to gain further understanding we performed single-probe STM experiment on a clean Ge(001)-c(4 × 2) surface area near a single monoatomic step-edge (Fig. 3a, with structural details in Supplementary Note 6).
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