Large dynamic perturbations of transient magnetic fields induced by heavy ion beams

Measurements of transient magnetic fields in Fe for Coulomb-excited²⁴Mg(2^↓)-ions at high velocity confirm strong attenuations as observed earller for single-electron²⁸Si ions. In a measurement in which the beam was stopped in a non-magnetic buffer layer sandwiched between the target and the Fe layer the perturbation was shown to result from the interaction of the heavy Ni beam with the ferromagnet. The attenuations seem to be correlated with the dE/dx of the beam-ions in the ferromagnet.     

Coulomb-interaction-induced incomplete shell filling in the hole system of InAs quantum dots

We have studied the hole charging spectra of self-assembled InAs quantum dots in perpendicular magnetic fields by capacitance-voltage spectroscopy. From the magnetic-field dependence of the individual peaks we conclude that the s-like ground state is completely filled with two holes but that the fourfold degenerate p shell is only half filled with two holes before the filling of the d shell starts. The resulting six-hole ground state is highly polarized. This incomplete shell filling can be explained by the large influence of the Coulomb interaction in this system.     

Tungsten oxide nanowire growth by chemically induced strain

We have investigated the formation of tungsten oxide nanowires under different chemical vapor deposition (CVD) conditions. We find that exposure of oxidized tungsten films to hydrogen and methane at 900 degrees C leads to the formation of a dense array of typically 10 nm diameter nanowires. Structural and chemical analysis shows that the wires are crystalline WO3. We propose a chemically driven whisker growth mechanism in which interfacial strain associated with the formation of tungsten carbide stimulates nanowire growth. This might be a general concept, applicable also to other nanowire systems.     

Thermal roughening of a thin film: A new type of roughening transition

It is found that an m = n = 1 mode with amplitude exceeding a certain threshold can lead to stochastic motion of energetic ions in tokamaks, the large orbit width particles (potatoes) being most easily affected. An n = 1 mode can redistribute particles also in the absence of stochasticity but only when the perturbation is quickly switched on/off, e.g., during a sawtooth crash. In the latter case, the perturbation results in a regular motion of particles around a certain helical orbit, at which a resonance driven by the mode but having no amplitude threshold takes place.     

Hot-electron effects in two-dimensional hopping with a large localization length

We have studied nonlinear effects in the resistance of a two-dimensional system with a large localization length on both sides of the crossover from weak to strong localization. It is shown that nonlinearity in the hopping regime is due to electron overheating rather than the field effects. This qualitatively new behavior is a signature of a two-dimensional hopping transport with a large localization length.     

Resolventenwachstum und Vollständigkeit meromorpher Operatoren in normierten Räumen

Ohne Zusammenfassung     

Die Destillation von tr?gerfreiem Ruthenium

Ohne Zusammenfassung