Atomic Hole Doping of Graphene

Graphene is an excellent candidate for the next generation of electronic materials due to the strict two-dimensionality of its electronic structure as well as the extremely high carrier mobility. A prerequisite for the development of graphene based electronics is the reliable control of the type and density of the charge carriers by external (gate) and internal (doping) means. While gating has been successfully demonstrated for graphene flakes and epitaxial graphene on silicon carbide, the development of reliable chemical doping methods turns out to be a real challenge. In particular hole doping is an unsolved issue. So far it has only been achieved with reactive molecular adsorbates, which are largely incompatible with any device technology. Here we show by angle-resolved photoemission spectroscopy that atomic doping of an epitaxial graphene layer on a silicon carbide substrate with bismuth, antimony or gold presents effective means of p-type doping. Not only is the atomic doping the method of choice for the internal control of the carrier density. In combination with the intrinsic n-type character of epitaxial graphene on SiC, the charge carriers can be tuned from electrons to holes, without affecting the conical band structure

Gamma-ray Emission from Classical Nova V392 Per: Measurements from Fermi and HAWC

This paper reports on the $\gamma$-ray properties of the 2018 Galactic novaV392 Per, spanning photon energies $\sim$0.1 GeV to 100 TeV by combiningobservations from the Fermi Gamma-ray Space Telescope and the HAWC Observatory.In one of the most rapidly evolving $\gamma$-ray signals yet observed for anova, GeV $\gamma$ rays with a power law spectrum with index $\Gamma = 2.0 \pm0.1$ were detected over eight days following V392 Per's optical maximum. HAWCobservations constrain the TeV $\gamma$-ray signal during this time and alsobefore and after. We observe no statistically significant evidence of TeV$\gamma$-ray emission from V392 Per, but present flux limits. Tests of theextension of the Fermi/LAT spectrum to energies above 5 TeV are disfavored by 2standard deviations (95\%) or more. We fit V392 Per's GeV $\gamma$ rays withhadronic acceleration models, incorporating optical observations, and comparethe calculations with HAWC limits.<br

Die Gestaltung der Arbeits- und Lebensbedingungen ein Beitrag zur Formierung und Entwicklung der Stammbelegschaft ; untersucht und dargestellt am Beispiel des VEB Kombinat Schwarze Pumpe

DB Leipzig(101) - Di 1980 B VD 91, T. 1, 2 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman