Thomas Schäpers

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We present results about the growth of GaAs/InAs core-shell nanowires (NWs) using molecular beam epitaxy. The core is grown via the Ga droplet-assisted growth mechanism. For a homogeneous growth of the InAs shell, the As(4) flux and substrate temperature are critical. The shell growth starts with InAs islands along the NW core, which increase in time and(More)
InN nanowires, grown by plasma-enhanced molecular beam epitaxy, were investigated by means of magnetotransport. By performing temperature-dependent transport measurements and current measurements on a large number of nanowires of different dimensions, it is proven that the carrier transport mainly takes place in a tube-like surface electron gas.(More)
Three-dimensional (3D) topological insulators are a new state of quantum matter, which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material. There have been various attempts to tune the Dirac point to a desired energetic position for(More)
We demonstrate the growth and structural characteristics of InAs nanowire junctions evidencing a transformation of the crystalline structure. The junctions are obtained without the use of catalyst particles. Morphological investigations of the junctions reveal three structures having an L-, T-, and X-shape. The formation mechanisms of these structures have(More)
We have modeled InAs nanowires using finite element methods considering the actual device geometry, the semiconducting nature of the channel and surface states, providing a comprehensive picture of charge distribution and gate action. The effective electrostatic gate width and screening effects are taken into account. A pivotal aspect is that the gate(More)
Back-gated InAs nanowire field-effect transistors are studied focusing on the formation of intrinsic quantum dots, i.e. dots not intentionally defined by electrodes. Such dots have been studied before, but the suggested explanations for their origin leave some open questions, which are addressed here. Stability diagrams of samples with different doping(More)
We compute analytically the weak (anti)localization correction to the Drude conductivity for electrons in tubular semiconductor systems of zinc-blende type. We include linear Rashba and Dresselhaus spin-orbit coupling (SOC) and compare wires of standard growth directions 〈100〉, 〈111〉, and 〈110〉. The motion on the quasi-twodimensional surface is considered(More)
InAs nanowires are grown epitaxially by catalyst-free metal organic vapor phase epitaxy and are subsequently positioned with a lateral accuracy of less than 1 μm using simple adhesion forces between the nanowires and an indium tip. The technique, requiring only an optical microscope, is used to place individual nanowires onto the corner of a cleaved-edge(More)
Caitlin Morgan, Maciej Misiorny, Dominik Metten, Sebastian Heedt, Thomas Schäpers, Claus M. Schneider, and Carola Meyer Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, D-52425 Jülich, Germany JARA—Fundamentals of Future Information Technologies, D-52425 Jülich, Germany Department of Microtechnology and Nanoscience MC2, Chalmers University of(More)
Pavel Vagner,* Peter Markoš, Martin Moško, and Thomas Schäpers Institut für Schichten und Grenzflächen, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia Department of Complex Physical Systems, Institute of Physics, Slovak Academy of Sciences,(More)