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Title

Two-probe STM/STS experiments performed on atomic wires and single molecules supported on Ge(001) surface

AuthorsKolmer, Marek; Brandimarte, Pedro; Zajac, Lukasz; Godlewski, Szymon; Kawai, Hiroyo; Frederiksen, Thomas; Engelund, Mads; García-Lekue, Aran; Lorente, Nicolás ; Lis, Jakub; Echavarren, Antonio M.; Joachim, Christian; Sánchez-Portal, Daniel ; Szymonski, Marek
Issue Date2018
CitationEuropean Symposium on Surface Science (2018)
AbstractDue to unprecedented precision reaching sub-picometers scanning probe microscopy (SPM) methods are currently the most popular and reliable tools for local characterization of atomic and single-molecule systems supported on surfaces of solids. However, direct determination of many functional properties, including especially electronic transport in prototypical planar atomic-scale devices, lies beyond the single-probe SPM approach. Recent technical advances provide multi-probe SPM instruments, which are able to operate on the same surface simultaneously with stability comparable to best cryogenic single-probe SPMs. In this work, we describe the full methodology behind atomically defined two-probe scanning tunneling microscopy and spectroscopy (STM/STS) experiments performed on model systems on the germanium (001) surface. Firstly, we discuss our methodology for fine relative positioning of two STM probes on Ge(001) and Ge(001):H surfaces with exact atomic precision and lateral probe to probe distances below 50 nm. That technical results opens possibility of direct testing of on-surface electron transport in a planar geometry. It is realized by a novel two-probe STS (TP-STS) methodology, in which both STM tips are kept in tunneling conditions above a grounded sample. By applying a small AC component to a varied DC bias voltage on one of the probes and by demodulation of resulting current signals on both of the probes, we extract corresponding dI1/dV1 (single-probe, vertical) and dI2/dV1 (two-probe, planar) STS signals. In this case of Ge(001) we show that the detection of TPSTS signal is related to quasi-ballistic hot-electron transport through one-dimensional π* states of Ge dimer-row wires located within bulk bang gap of the surface. Our two-probe experimental results are corroborated by first-principles calculations combining the nonequilibrium Green's function (NEGF) formalism with density function theory (DFT) in a fourterminal setup. Finally, we present a non-local switching of single trinaphthylene molecule adsorbed on Ge(001) surface. The switching is induced by hot electrons injection into discussed π* states of Ge dimer-rows. Here by taking the advantage of two-probe STM configuration we observe “in-situ” non-local molecule switching using one of the probes as a source of hot electrons injected into surface states and the other as a detector of a molecule motion.
DescriptionResumen del trabajo presentado al Symposium on Surface Science (3S), celebrado en St. Christoph am Arlberg (Austria) del 25 de febrero al 10 de marzo de 2018.
URIhttp://hdl.handle.net/10261/179414
Appears in Collections:(CFM) Comunicaciones congresos
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