Research Article


2018, 11(11): 5924–5934


Investigation of charge carrier depletion in freestanding nanowires by a multi-probe scanning tunneling microscope

Andreas Ngelein1 (*), Matthias Steidl1, Stefan Korte2,3, Bert Voigtlnder2,3, Werner Prost4, Peter Kleinschmidt1, and Thomas Hannappel1 (*)

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1 Technische Universitt Ilmenau, Institut für Physik, 98693 Ilmenau, Germany
2 Peter Grünberg Institut (PGI-3,) Forschungszentrum Jülich, 52425 Jülich, Germany
3 JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich, Germany
4 University of Duisburg-Essen, Solid State Electronics Department, 47057 Duisburg, Germany

Keywords: multi-tip scanning tunneling microscopy (MT-STM), electrical characterization, nanowires, charge carrier depletion, oxidation
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ABSTRACT Profiling of the electrical properties of nanowires (NWs) and NW heterocontacts with high spatial resolution is a challenge for any application and advanced NW device development. For appropriate NW analysis, we have established a four-point prober, which is combined in vacuo with a state-of-the-art vaporliquid-solid preparation, enabling contamination-free NW characterization with high spatial resolution. With this ultrahigh-vacuum-based multi-tip scanning tunneling microscopy (MT-STM), we obtained the resistance and doping profiles of freestanding NWs, along with surface-sensitive information. Our in-system 4-probe STM approach decreased the detection limit for low dopant concentrations to the depleted case in upright standing NWs, while increasing the spatial resolution and considering radial depletion regions, which may originate from surface changes. Accordingly, the surface potential of oxide-free GaAs NW {112} facets has been estimated to be lower than 20 mV, indicating a NW surface with very low surface state density.
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Investigation of charge carrier depletion in freestanding nanowires by a multi-probe scanning tunneling microscope. Nano Res. 2018, 11(11): 5924–5934

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