Gunther Springholz

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Ge growth on high-indexed Si (1110) is shown to result in the spontaneous formation of a perfectly {105} faceted one-dimensional nanoripple structure. This evolution differs from the usual Stranski-Krastanow growth mode because from initial ripple seeds a faceted Ge layer is formed that extends down to the heterointerface. Ab initio calculations reveal that(More)
Dirac fermions in condensed matter physics hold great promise for novel fundamental physics, quantum devices and data storage applications. IV-VI semiconductors, in the inverted regime, have been recently shown to exhibit massless topological surface Dirac fermions protected by crystalline symmetry, as well as massive bulk Dirac fermions. Under a strong(More)
SiGe heteroepitaxy on vicinal Si (1 1 10) is studied as a model system for one-dimensional (1D) to three-dimensional growth mode transitions. By in situ scanning tunneling microscopy it is shown that the 1D-3D transition proceeds smoothly from perfectly facetted 1D nanoripples to coarsened superripples, tadpoles, asymmetric domes, and barns without(More)
The long-term stability of functional properties of topological insulator materials is crucial for the operation of future topological insulator based devices. Water and oxygen have been reported to be the main sources of surface deterioration by chemical reactions. In the present work, we investigate the behavior of the topological surface states on Bi2X3(More)
For the prototypical Ge/Si(001) system, we show that at high growth temperature a new type of Stranski-Krastanow islands is formed with side facets steeper than {111} and high aspect ratio. Nano-goniometric analysis of the island shapes reveals the presence of six new facet groups in addition to those previously found for dome or barn-shaped islands. Due to(More)
Magnetic doping is expected to open a band gap at the Dirac point of topological insulators by breaking time-reversal symmetry and to enable novel topological phases. Epitaxial (Bi(1-x)Mn(x))2Se3 is a prototypical magnetic topological insulator with a pronounced surface band gap of ∼100 meV. We show that this gap is neither due to ferromagnetic order in the(More)
The temperature dependences of the magnetizations of individual atomic layers across an epitaxial antiferromagnetic EuTe film were derived from virtually background-free magnetic Bragg peaks with pronounced Laue oscillations recorded with soft x rays at the Eu-M5 resonance. The magnetizations of the outermost layers decrease significantly differently from(More)
Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable(More)
Epitaxial growth of topological insulator bismuth telluride by molecular beam epitaxy onto BaF2 (111) substrates is studied using Bi2Te3 and Te as source materials. By changing the beam flux composition, different stoichiometric phases are obtained, resulting in high quality Bi2Te3 and Bi1Te1 epilayers as shown by Raman spectroscopy and high-resolution(More)
Self-assembly of colloidal nanocrystals and other nanosized building blocks has led to numerous large-scale and well-ordered superstructures. To quantify the superlattice quality we present a simple and efficient method, based on analysis of the autocorrelation function to determine characteristic order parameters for short-range and long-range ordering.(More)