Dagmar Gerthsen

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Numerical simulations of a near-infrared negative-index metama-terial (NIM) slab consisting of multiple layers of perforated metal-dielectric stacks exhibiting a small imaginary part of the index over the wavelength range for negative refraction are presented. A consistent effective index is obtained using both scattering matrix and modal analysis(More)
In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is(More)
We observe ultraviolet photoluminescence from sputtered ZnO quantum dots which are fabricated with no annealing steps. The nanocrystals are embedded in amorphous SiO2 and exhibit a narrow size distribution of 3.5 ± 0.6 nm. Photoluminescence and transmittance measurements show a shift of ultraviolet emission and absorption of the dots compared to bulk ZnO(More)
The effect of growth temperature on AlAs/GaAs resonant tunneling diodes Formation of unstrained Si 1-x Ge x layers by high-dose 74 Ge ion implantation in SIMOX High-resolution electron microscopy and X-ray diffraction characterization of alternately strained (GaAs) n (GaP) m (GaAs) n (InP) m superlattices grown by atomic layer epitaxy Structural properties(More)
Photonic signal processing requires efficient on-chip light sources with higher modulation bandwidths. Today's conventional fastest semiconductor diode lasers exhibit modulation speeds only on the order of a few tens of GHz due to gain compression effects and parasitic electrical capacitances. Here we theoretically show an electrically-driven carbon(More)
Structure analysis of the cell-penetrating peptide transportan 10 (TP10) revealed an exemplary range of different conformations in the membrane-bound state. The bipartite peptide (derived N-terminally from galanin and C-terminally from mastoparan) was found to exhibit prominent characteristics of (i) amphiphilic α-helices, (ii) intrinsically disordered(More)
We report on progress in growth and applications of submonolayer (SML) quantum dots (QDs) in high-speed vertical-cavity surface-emitting lasers (VCSELs). SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs(More)
  • Ingo Tischer, Matthias Hocker, Benjamin Neuschl, Manfred Madel, Martin Feneberg, Martin Schirra +16 others
  • 2015
Group III nitrides are promising materials for light emitting diodes (LEDs). The occurrence of structural defects strongly affects the efficiency of these LEDs. We investigate the optical properties of basal plane stacking faults (BFSs), and the assignment of specific spectral features to distinct defect types by direct correlation of localized emission(More)
Zinc oxide (ZnO) nanocrystals (NCs) with high crystalline quality were prepared via radio-frequency magnetron sputtering as a SiO(2)/ZnO/SiO(2) trilayer on Si(100) and Al(2)O(3)(0001) substrates with an intermediate in situ annealing step. Transmission electron microscopy reveals a uniform dispersion of ZnO NCs in the amorphous SiO(2) matrix with typical(More)