Electronic and Geometric Corrugation of Periodically Rippled, Self-nanostructured Graphene Epitaxially Grown on Ru(0001)

Graphene epitaxially grown on Ru(0001) displays a remarkably ordered pattern of hills and valleys in Scanning Tunneling Microscopy (STM) images. To which extent the observed "ripples" are structural or electronic in origin have been much disputed recently. A combination of ultrahigh resolution STM images and Helium Atom diffraction data shows that i) the graphene lattice is rotated with respect to the lattice of Ru and ii) the structural corrugation as determined from He diffraction is substantially smaller (0.015 nm) than predicted (0.15 nm) or reported from X-Ray Diffraction or Low Energy Electron Diffraction. The electronic corrugation, on the contrary, is strong enough to invert the contrast between hills and valleys above +2.6 V as new, spatially localized electronic states enter the energy window of the STM. The large electronic corrugation results in a nanostructured periodic landscape of electron and holes pockets.Comment: 16 pages, 6 figure

Tunable magnetic properties of arrays of Fe(110) nanowires grown on kinetically-grooved W(110) self-organized templates

We report a detailed magnetic study of a new type of self-organized nanowires disclosed briefly previously [B. Borca et al., Appl. Phys. Lett. 90, 142507 (2007)]. The templates, prepared on sapphire wafers in a kinetically-limited regime, consist of uniaxially-grooved W(110) surfaces, with a lateral period here tuned to 15nm. Fe deposition leads to the formation of (110) 7 nm-wide wires located at the bottom of the grooves. The effect of capping layers (Mo, Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was studied. Significant discrepancies with figures known for thin flat films are evidenced and discussed in terms of step anisotropy and strain-dependent surface anisotropy. Demagnetizing coeffcients of cylinders with a triangular isosceles cross-section have also been calculated, to estimate the contribution of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the interface element was used to tune the blocking temperature of the wires, here from 50K to 200 K

Kinetic self-organization of trenched templates for the fabrication of versatile ferromagnetic nanowires

We have self-organized versatile magnetic nanowires, ie with variable period and adjustable magnetic anisotropy energy (MAE). First, using the kinetic roughening of W(110) uniaxial templates of trenches were grown on commercial Sapphire wafers. Unlike most templates used for self-organization, those have a variable period, 4-12nm are demonstrated here. Fe deposition then results in the formation of wires in the trenches. The magnitude of MAE could be engineered up or down by changing the capping- or underlayer, in turn affecting the mean superparamagnetic temperature, raised to 175K so far.Comment: 3 page

Growth and magnetism of self-organized arrays of Fe(110) wires formed by deposition on kinetically grooved W(110)

Homoepitaxy of W(110) and Mo(110) is performed in a kinetically-limited regime to yield a nanotemplate in the form of a uniaxial array of hills and grooves aligned along the [001] direction. The topography and organization of the grooves were studied with RHEED and STM. The nanofacets, of type {210}, are tilted 18° away from (110). The lateral period could be varied from 4 to 12nm by tuning the deposition temperature. Magnetic nanowires were formed in the grooves by deposition of Fe at 150°C on such templates. Fe/W wires display an easy axis along [001] and a mean blocking temperature Tb=100KComment: Proceedings of ECOSS 2006 (Paris

CL4. CAM-LDA0: The Reincarnation of the Local Density Approximation

Kohn-Sham Density Functional Theory (KS-DFT) is the most popular electronic structure method applied throughout science and engineering. The exchange-correlation (XC) local density approximation (LDA) was the earliest density functional used to investi-gate the electronic structure of chemical systems in KS-DFT. Since then, the LDA has been the bedrock of the field of density functional development. In this contribution, we discuss the roles of the non-local exchange and the local-density approximation in the improvement of the quality of the fundamental gap, and in the enhancement excitation-energy estimations. We suggest that the combination of these two concepts is dominant for the calculation of excitation energies of molecules in the optical regime and beyond. As an illustration of the wide range of possibilities created by our work, we report CAM-LDA0: a three-parameter functional, with 1/4 global and 1/2 long-range Hartree-Fock interaction, respectively; a range separation factor of 1/3; and pure LDA exchange and correlation. We show that CAM-LDA0 matches the accuracy of CAM-B3LYP for electronic excitations, with the advantage of reduced computational cost due to the omission of the generalized-gradient corrections. These findings have been recently reported in the The Journal of Physical Chemistry A [1]. Carlos H. Borca, Purdue University Martín A. Mosquera, Northwestern University Mark A. Ratner, Northwestern University George C. Schatz, Northwestern Universit

A Possible Managerial Approach for Internal Organizational Communication Characterization

AbstractThe paper will present a proposed approach for the organizational communication diagnosis. Based on relevant references, the context and the motivation of the research will be outlined. The proposed methodology will be applied for the characterization of the communication style (for administrative staff, including top management team) in the case of an extant company. The research conclusion (as SWOT matrix) underlines the improvements that should be made in accordance to the criteria described in order to gain organizational communication success