In-situ surface technique analyses and ex-situ characterization of Si1-xGex epilayers grown on Si(001)-2 ×1 by molecular beam epitaxy

Si1-xGex epilayers grown by Molecular Beam Epitaxy on Si(001) at 400 ○C have been analyzed in-situ by surface techniques such as X-ray and Ultraviolet Photoelectron Spectroscopies (XPS and UPS), Low Energy Electron Diffraction (LEED) and photoelectron diffraction (XPD). The Ge surface concentrations (x) obtained from the ratios of Ge and Si core level intensities are systematically higher than those obtained by the respective evaporation fluxes. This indicates a Ge enrichment in the first overlayers confirmed by Ge-like UPS valence band spectra. The structured crystallographic character of the epilayers is ascertained by LEED and XPD polar scans in the (100) plane since the Ge Auger LMM and the Si 2p XPD intensity patterns from the Si1-xGex epilayers are identical to those of the Si substrate. The residual stress in the epilayer is determined by ex-situ X-ray diffraction (XRD) which also allows, as Rutherford Back Scattering (RBS), Ge concentration determinations

Symmetry of standing waves generated by a point defect in epitaxial graphene

Using scanning tunneling microscopy (STM) and Fourier Transform STM (FT-STM), we have studied a point defect in an epitaxial graphene sample grown on silicon carbide substrate. This analysis allows us to extract the quasiparticle energy dispersion, and to give a first experimental proof of the validity of Fermi liquid theory in graphene for a wide range of energies from -800 meV to +800 meV. We also find evidence of a strong threefold anisotropy in the standing waves generated by the defect. We discuss possible relations between this anisotropy, the chirality of the electrons, and the asymmetry between graphene's two sublattices. All experimental measurements are compared and related to theoretical T-matrix calculations.Comment: 4 pages, 4 figure

Repurpose 2D Character Animations for a VR Environment Using BDH Shape Interpolation.

Virtual Reality technology has spread rapidly in recent years. However, its growth risks ending soon due to the absence of quality content, except for few exceptions. We present an original framework that allows artists to use 2D characters and animations in a 3D Virtual Reality environment, in order to give an easier access to the production of content for the platform. In traditional platforms, 2D animation represents a more economic and immediate alternative to 3D. The challenge in adapting 2D characters to a 3D environment is to interpret the missing depth information. A 2D character is actually flat, so there is not any depth information, and every body part is at the same level of the others. We exploit mesh interpolation, billboarding and parallax scrolling to simulate the depth between each body segment of the character. We have developed a prototype of the system, and extensive tests with a 2D animation production show the effectiveness of our framework

Fourier Transform Scanning Tunneling Spectroscopy: the possibility to obtain constant energy maps and the band dispersion using a local measurement

We present here an overview of the Fourier Transform Scanning Tunneling spectroscopy technique (FT-STS). This technique allows one to probe the electronic properties of a two-dimensional system by analyzing the standing waves formed in the vicinity of defects. We review both the experimental and theoretical aspects of this approach, basing our analysis on some of our previous results, as well as on other results described in the literature. We explain how the topology of the constant energy maps can be deduced from the FT of dI/dV map images which exhibit standing waves patterns. We show that not only the position of the features observed in the FT maps, but also their shape can be explained using different theoretical models of different levels of approximation. Thus, starting with the classical and well known expression of the Lindhard susceptibility which describes the screening of electron in a free electron gas, we show that from the momentum dependence of the susceptibility we can deduce the topology of the constant energy maps in a joint density of states approximation (JDOS). We describe how some of the specific features predicted by the JDOS are (or are not) observed experimentally in the FT maps. The role of the phase factors which are neglected in the rough JDOS approximation is described using the stationary phase conditions. We present also the technique of the T-matrix approximation, which takes into account accurately these phase factors. This technique has been successfully applied to normal metals, as well as to systems with more complicated constant energy contours. We present results recently obtained on graphene systems which demonstrate the power of this technique, and the usefulness of local measurements for determining the band structure, the map of the Fermi energy and the constant-energy maps.Comment: 33 pages, 15 figures; invited review article, to appear in Journal of Physics D: Applied Physic

Safety and Efficacy of Risuteganib in Intermediate Non-exudative Age-Related Macular Degeneration

Purpose : Risuteganib is a small synthetic peptide that regulates select integrin functions involved in the pathogenesis of dry age-related macular degeneration (AMD). This study evaluated the safety and efficay of risuteganib for the treatment of dry AMD. Methods : Randomized, double-masked, placebo-controlled Phase 2 study in eyes with intermediate dry AMD presenting with best-corrected visual acuity (BCVA) between 20/40-20/200 was conducted across multiple centers in the United States. Patients were randomized to receive either intravitreal 1.0mg risuteganib or sham injection at baseline. At week 16, patients in the risuteganib group received a second dose and the sham group crossed over and receive a single dose of 1.0mg risuteganib. The primary endpoint was the percentage of population with ≥ 8 letters BCVA gain from baseline to week 28 in 1.0mg risuteganib vs baseline to week 12 for sham. Results : Forty-five patients were enrolled in the study. At baseline, mean patient age was 78.8 and 75.9 years and mean baseline BCVA was 67.1 and 64.4 letters in the sham and risuteganib groups, respectively. The primary endpoint was met; 48% of patients in the risuteganib group at week 28 and 7% of patients in the sham group at week 12 gained > 8 letters from baseline (p=0.013). Of the risuteganib treated patients, 20% gained > 15 letters at week 28; no patients in the sham group at week 12 had this gain. On a post-hoc masked analysis by 2 independent reading centers, greater outer retinal and photoreceptor thickness and volume and smaller ellipsoid zone defect area in the central 1 mm zone at baseline were associated with increased BCVA response to risuteganib. Risuteganib demonstrated a good safety profile in this study. Conclusions : Risuteganib showed significant benefit over sham in patients with dry AMD with respect to proportion of patients gaining > 8 letters of BCVA from baseline. Furthermore, post hoc analysis provides preliminary insights into baseline anatomic features that may help to determine likelihood of BCVA response to risuteganib. These findings will be confirmed in an upcoming larger trial