Cathodoluminescence investigations of RIE-induced defects in InP

Cathodoluminescence (CL) measurements have been performed to characterize defects in InP created by reactive ion etching (RIE) in a CH₄/H₂/Ar plasma. Etching of semi-insulating InP:Fe leads to an increase of CL intensity. After etching of undoped, n-type InP a reduction of band-edge as well as band-acceptor/donor-acceptor-pair emission intensity is detected. No additional emission lines due to etching-induced defects have been detected in the spectral range examined. After a few minutes of electron beam injection the band-edge luminescence recovers to its initial value. Using donor-bound exciton emission, which is especially affected by RIE, mapping of these defects is possible, showing homogeneous defect distribution. In conjunction with other measurements (conductivity, photoluminescence, electron-beam-induced current, Raman scattering, Auger electron spectroscopy depth profiling) these results indicate a nonradiative, donor-like defect created by RIE.     

Untersuchung von Mehl und Getreide

Ohne Zusammenfassung     

Heat Trace and Spectral Action on the Standard Podleś Sphere

We give a new definition of dimension spectrum for non-regular spectral triples and compute the exact (i.e., not only the asymptotics) heat-trace of standard Podle? spheres \({S^2_q}\) for 0 < q < 1, study its behaviour when \({q\to 1}\) , and fully compute its exact spectral action for an explicit class of cut-off functions.     

Scattering of hydrogen and helium from cesiated surfaces

Hydrogen and helium ion beams with energies of 1 to 15 keV have been reflected from Cs-covered Ni surfaces at normal incidence. For hydrogen there are surface peaks in the positive fraction and surface minima in the negative fraction, a result very different from that observed with other materials. The charged fractions of both hydrogen and helium depend on the thickness of the Cs layer. Some results for scattering of hydrogen at glancing angles are presented.     

Grafting of polytetrahydrofuran from neoprene W in the presence of perchlorate salts

Silver, mercury, and lead perchlorates can be used to prepare graft copolymers of polytetrahydrofuran from neoprene. Iron and aluminum perchlorates lead to graft copolymers but the conversion is low. The most efficient graft copolymerizations are obtained at high salt-to-neoprene ratios, long reaction times, and low monomer-to-neoprene concentration ratios. Very surprisingly, high initial monomer-to-neoprene concentration ratios lead to low graft copolymerization efficiencies.     

Synthesis and characterization of semifluorinated polymers and block copolymers

The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains.