Oliver Warschkow

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The ability to control matter at the atomic scale and build devices with atomic precision is central to nanotechnology. The scanning tunnelling microscope can manipulate individual atoms and molecules on surfaces, but the manipulation of silicon to make atomic-scale logic circuits has been hampered by the covalent nature of its bonds. Resist-based(More)
Oxide surfaces are important for applications in catalysis and thin film growth. An important frontier in solid-state inorganic chemistry is the prediction of the surface structure of an oxide. Comparatively little is known about atomic arrangements at oxide surfaces at present, and there has been considerable discussion concerning the forces that control(More)
We report the solution of the c(4 x 2) reconstruction of SrTiO(3) (001), obtained through a combination of high-resolution transmission electron microscopy, direct methods analysis, and density functional theory. The structure is characterized by a single overlayer of TiO(2) stoichiometry in which TiO(5) polyhedra are arranged into edge-shared structures,(More)
Density functional calculations are performed to identify features observed in STM experiments after phosphine (PH3) dosing of the Si(001) surface. On the basis of a comprehensive survey of possible structures, energetics, and simulated STM images, three prominent STM features are assigned to structures containing surface bound PH2, PH, and P, respectively.(More)
We have recently reported structure solutions for the (2 · 1) and c(4 · 2) reconstructions of SrTiO 3 (0 0 1) based on high-resolution electron microscopy, direct methods analysis of diffraction data and density functional theory. Both reconstructions were found to be TiO 2-rich and feature a single overlayer of TiO 2 stoichiometry on top of a bulk-like TiO(More)
The c͑6 ϫ 2͒ is a reconstruction of the SrTiO 3 ͑001͒ surface that is formed between 1050 and 1100 ° C in oxidizing annealing conditions. This work proposes a model for the atomic structure for the c͑6 ϫ 2͒ obtained through a combination of results from transmission electron diffraction, surface x-ray diffraction, direct methods analysis, computational(More)
Characterization of lead substitution for calcium in hydroxyapatite (CaHA) is carried out, using experimental techniques and Density Functional theoretical (DFT) analyses. Theoretical modeling is used to obtain information of the Pb chemical environment for occupancy at either Ca(I) or Ca(II) sites of CaHA. Effects of the larger ionic radius of Pb(+2)(More)
Transmission electron diffraction (TED) combined with direct methods have been used to study the sqrt[3]xsqrt[3]R30 degrees reconstruction on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric and is terminated by a single magnesium atom. A charge-compensating electron hole is localized in the next(More)
Extending chip performance beyond current limits of miniaturisation requires new materials and functionalities that integrate well with the silicon platform. Germanium fits these requirements and has been proposed as a high-mobility channel material, a light emitting medium in silicon-integrated lasers, and a plasmonic conductor for bio-sensing. Common to(More)
We present a single electron transistor (SET) based on an individual phosphorus dopant atom in an epitaxial silicon environment. Using scanning tunneling microscope (STM) hydrogen lithography, the single impurity is deterministically placed with a spatial accuracy of ±1 lattice site within a donor-based transport device. Low temperature transport(More)