Synthesis of cubic zirconium and hafnium nitride having Th3P4 structure

High-pressure synthesis is a powerful method for the preparation of novel materials with high elastic moduli and hardness. Additionally, such materials may exhibit interesting thermal, optoelectronic, semiconductuing, magnetic or superconducting properties. Here, we report on the high-pressure synthesis of zirconium and hafnium nitrides with the stoichiometry M3N4, where M = Zr, Hf. Synthesis experiments were performed in a laser-heated diamond anvil cell at pressures up to 18 GPa and temperatures up to 3,000 K. We observed formation of cubic Zr3N4 and Hf3N4 (c-M3N4) with a Th3P4-structure, where M-cations are eightfold coordinated by N anions. The c-M3N4 phases are the first binary nitrides with such a high coordination number. Both compounds exhibit high bulk moduli around 250 GPa, which indicates high hardness. Moreover, the new nitrides, c-Zr3N4 and c-Hf3N4, may be the first members of a larger group of transition metal and/or lanthanide nitrides with interesting ferromagnetic or superconducting behaviour.     

Messbare IT-Sicherheit

Zusammenfassung  Der vom Bundesamt für Sicherheit in der Informationstechnik (BSI) entwickelte Ansatz des IT-Grundschutzes war bereits Gegenstand von Beitr?gen in der DuD. Inzwischen hat das „Grundschutzhandbuch“ Eingang in die internationale Standard-Familie ISO 2700x gefunden. Der Autor berichtet über die Erfahrungen mit den ersten durchgeführten Zertifizierungen nach dem neuen ISO-Standard auf der Basis von IT-Grundschutz. Dr. Gerhard Weck: Leiter IT Security Consulting. der INFODAS GmbH K?ln. Derzeitiger Arbeitsschwerpunkt: Entwicklung und Vermittlung von Sicherheitskonzepten. Lizenzierter ISO 27001/IT-Grundschutz-Auditor. Autor bzw. Koautor mehrerer Bücher. Fellow der GI. Mitglied des Pr?sidiums-Arbeitskreises „Datenschutz und IT-Sicherheit“ der GI, Sprecher der Security SIG der HP User Society DECUS München e.V.     

Simulation of quantum-ballistic nanoswitches

A two-dimensional model based on the solution of the Schrödinger-Poisson system in effective-mass formulation is proposed for the calculation of quantum-ballistic transport processes in nanoswitch structures. The method is appropriate to properly describe the strong confinement of the electrons in the heterostructure. Using scattering boundary conditions an energy-dependent transmission matrix is calculated that allows us to determine the total charge density of all electrons injected into the device by integration over energy. In this approach space charge effects are self-consistently taken into account. The practicality of the model for numerical simulation is demonstrated with reference to measured data for various device geometries. We find that for device structures such as the Y-branch switch non-linear effects are of crucial importance.