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MM: Fachverband Metall- und Materialphysik
MM 40: Nanomaterials III
MM 40.4: Talk
Thursday, March 17, 2011, 17:00–17:15, IFW B
3D imaging of electrostatic potentials in nanostructures with electron holographic tomography — •Wolf Daniel1, Lubk Axel2, and Lichte Hannes1 — 1Triebenberg Laboratory, Institute of Structure Physics, Technische Universität Dresden, 01062 Dresden, Germany — 2CEMES-CNRS, 29 rue J. Marvig, 31055 Toulouse, France
Electron-holographic tomography (EHT), that is, the combination of off-axis electron holography (EH) with electron tomography (ET), allows the quantitative 3D mapping of electrostatic potentials and magnetostatic vector fields with a resolution of a few (5-10) nanometers. The 3D potential offers the outer (morphology) and inner structure, as well as the mean inner potential (MIP) of the nano object. This is shown on epitaxially grown nanowires (NWs) of GaAs and AlGaAs. The 3D morphology is studied using the corresponding iso-surfaces of the 3D potential: The facets on the nanowires surface allow conclusions about the crystalline structure. Moreover, the reconstructed 3D potential of a AlGaAs/GaAs NW clearly shows its core/shell structure due to the MIP difference between GaAs and AlGaAs of 0.61 V. For doped semiconductor structures with pn-junctions (e.g. transistors) the potential distribution, reconstructed by EHT, also provides access to the built-in voltage across the pn-junction. The built-in voltage Δ Vpn can be analyzed in 3D and measured without projection and surface effects (e.g. dead layers) within the sample. The measurements of Δ Vpn in three needle-shaped specimens, prepared by FIB, yield for two silicon needles 1.0 V and 0.5 V, and for a germanium needle 0.4 V.