2024-03-28T10:34:08Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1796412020-05-25T15:05:46Zcom_10261_115com_10261_3col_10261_494
Kolmer, Marek
Brandimarte, Pedro
Zuzak, Rafał
Godlewski, Szymon
Kawai, Hiroyo
Frederiksen, Thomas
Engelund, Mads
García-Lekue, Aran
Lis, Jakub
Joachim, Christian
Sánchez-Portal, Daniel
Szymonski, Marek
2019-04-09T08:53:53Z
2019-04-09T08:53:53Z
2018
International Conference on Nanoscience + Technology (2018)
http://hdl.handle.net/10261/179641
http://dx.doi.org/10.13039/501100000780
Due to unprecedented precision reaching 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/spectroscopy (2P-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 atomic-scale systems. Here, it is realized by a novel 2P-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 the second probe, we extract corresponding transconductance dI2/dV1 2P-STS
signal. In the case of the Ge(001) surface we show that the detection of transconductance is related
to coherent hot-electron transport through quasi one-dimensional π* states of Ge dimer-rows located
within bulk bang gap of the surface. Our two-probe experimental results are corroborated by first-principles calculations combining the non-equilibrium Green’s function (NEGF) formalism with density function theory (DFT) in a four-terminal setup.
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Two-probe scanning tunneling spectroscopy: determination of transconductance in planar atomic structures
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