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

Entwurf von SPS-Steuerungen am virtuellen Maschinenprototyp

Normally, development and test of PLC programs can only be done if the machine itself is available. A solution is going to be presented, which allows simulating the behavior of the machine already during construction. At first the required machine model has to be constructed, which requires additional efforts. To gain maximal profit the model should be usable for different problems during the design process. The presented procedure shows the stepwise refinement of the machine model starting from the concept phase, through dimensioning of the drive and the controls up to the virtual start-u on the PLC

Model based virtual startup of automation systems

This paper deals with the model generation for automation systems. A generic solution is presented, which analyses existing Computer Aided Engineering CAE) documents and thereof automatically generates simulation models. They are described as Modelica models and use a special library, customized for the automation branch. It contains common elements which can be parameterized with very few efforts. Additional components for the communication to the control are available. They support several widely accepted technologies like OPC, Profibus, Profinet, analog and digital signals. The generation process focuses on being as automated as possible. It is a general approach, which could be applied to various types of simulation with different levels of detail. Its integration into a software prototype shows the feasibility and provides first practical feedback