Cyclotron resonance and photoluminescence studies of dilute GaAsN in magnetic fields up to 62 Tesla

In this thesis, we investigate optical and electrical properties of dilute nitride semiconductors GaAsN in pulsed magnetic fields up to 62 T. For the most part, the experiments are performed at the Dresden High Magnetic Field Laboratory (HLD). In the first part of this thesis, the electron effective mass of GaAsN is determined with a direct method for the first time. Cyclotron resonance (CR) absorption spectroscopy is performed in Si-doped GaAsN epilayers with a nitrogen content up to 0.2%. For the CR absorption study, we use the combination of the free-electron laser FELBE and pulsed magnetic fields at the HLD, both located at the Helmholtz-Zentrum Dresden-Rossendorf. A slight increase of the CR electron effective mass with N content is obtained. This result is in excellent agreement with calculations based on the band anticrossing model and the empirical tight-binding method. We also find an increase of the band nonparabolicity with increasing N concentration in agreement with our calculations of the energy dependent momentum effective mass. In the second part of this thesis, the photoluminescence (PL) characteristics of intrinsic GaAsN and n-doped GaAsN:Si is studied. The PL of intrinsic and very dilute GaAsN is characterized by both GaAs-related transitions and N-induced features. These distinct peaks merge into a broad spectral band of localized excitons (LEs) when the N content is increased. This so-called LE-band exhibits a partially delocalized character because of overlapping exciton wave functions and an efficient interexcitonic population transfer. Merged spectra dominate the PL of all Si-doped GaAsN samples. They have contributions of free and localized excitons and are consequently blue-shifted with respect to LE-bands of intrinsic GaAsN. The highly merged PL profiles of GaAsN:Si are studied systematically for the first time with temperature-dependent time-resolved PL. The PL decay is predominantly monoexponential and has a strong energy dispersion. In comparison to formerly reported values of intrinsic GaAsN epilayers, the determined decay times of GaAsN:Si are reduced by a factor of 10 because of enhanced Shockley-Read-Hall and possibly Auger recombinations. In the third part of this thesis, intrinsic and Si-doped GaAsN are investigated with magneto-PL in fields up to 62 T. A magneto-PL setup for pulsed magnetic fields of the HLD was built for this purpose. The blue-shift of LE-bands is studied in high magnetic fields in order to investigate its delocalized character. The blue-shift is diminished in intrinsic GaAsN at higher temperatures, which indicates that the interexcitonic population transfer is only active below a critical temperature 20 K < T < 50 K. A similar increase of the temperature has no significant impact on the partially delocalized character of the merged spectral band of GaAsN:Si. We conclude that the interexcitonic transfer of Si-doped GaAsN is more complex than in undoped GaAsN. In order to determine reduced masses of undoped GaAsN and GaAs:Si, the field-induced shift of the free exciton transition is studied in the high-field limit. We find an excellent agreement of GaAs:Si with a formerly published value of intrinsic GaAs which was determined with the same method. In both cases, the reduced mass values are enhanced by 20% in comparison to the accepted reduced mass values of GaAs. The determined GaAsN masses are 1.5 times larger than in GaAs:Si and match the rising trend of formerly reported electron effective masses of GaAsN

Freiheit zu ökumenischer eucharistischer gastfreundschaft/zur offenen kommunion

The paper is pleading for ecumenical liberty in favour of an epicletic-pneumatological understanding of the Lord’s Supper. After a short review of the last 70 years in the Protestant/Roman Catholic ecumenical relation in this regard, the main part treats the following: The presence of Christ in Word and Sacrament tending to the rediscovery of the Epiclesis. The final position is founded in an epicletic prayer of the so called ‘kurpfälzische Kirchenordnung 1563’, that underlines the fundamental liturgical unity of the essentials of the Eucharist: 1) The institution by the Lord, 1 Cor 11:23-25; 2) The interpretation of St. Paul, 1 Cor 11:26; 3) The invitation to Holy communion, Lc 14, 17 / Ps 34,9. This means unity in rite administrare (CA VII)

Calvins Sozialethik und der Kapitalismus

Calvin’s social ethics and the origin of modem CapitalismThis paper starts off by introducing the prejudices against the mentioned theme and its continuing effects, and stresses in the conclusion that the so-called Max Weber thesis was corrected by Weber himself. He explained its validity more in terms of seventeenth-century Puritanism than for its direct connection to the social doctrine of Calvin. The second heading reports the discussion and refutation of the Max Weber thesis in sociological, historical and theological literature. Calvin’s work on social-ethics is also honoured. The concluding ten theses sum up the importance of Calvin’s fundamental social-ethics for the solution of Geneva’s economic problems

Analyzing the regional long-term development of the German power system using a nodal pricing approach

This work presents an optimizing energy systems model, which is used to assess the regional long-term development of the German power system until 2030. The main decision criteria for a geographically optimal power plant expansion are the locational marginal costs of electricity supply. They are determined by using a DC power flow model based nodal pricing approach. The most important results are the cost-minimizing regional power station expansions as well as the regional costs of power supply

Entwickeln einer Zielpunktstrategie und Flussdichteprognose für den modularen Hochleistungsstrahler des DLR in Jülich

Für den modularen Hochleistungsstrahler in Jülich soll mit dem Raytracing-Programm OptiCAD eine Zielpunkt-strategie erarbeitet werden. Es sollen verschiedene Flussdichten auf Targets verschiedener Größe abgebildet werden

Showing the invisible – documentation and research on the Roman Domitilla catacomb, based on image laser scanning and 3D modelling

The possibilities offered by new technologies do not automatically substitute for traditional techniques. Particularly in the collaboration between humanities and natural sciences, not all that is technically possible is also helpful for a study. In this paper, an archaeological project is presented that connects both solid basic research and the newest technologies, offering a new way of perceiving historical space by creating three-dimensional virtual reality models. An overview of the technical aspects of the first year of the Domitilla project is presented: the first part introduces the catacomb, previous studies and the present research concept, whilst the second part reports on the strategy and the initial results of the documentation

Kapazitätsmessung eines verdeckten Kanals über HTTP

Wir beschreiben die Implementierung eines einfachen verdeckten Zeitkanals über HTTP und evaluieren dessen Kapazität im Internet. Im Experiment kommunizierte ein leicht modifizierter Apache-Webserver mit einem selbst geschriebenen HTTP-Proxy auf der Seite des Clients. Optimiert man den Kanal auf Fehlerfreiheit, können 3 Bit/s übertragen werden; akzeptiert man bis zu 10% Fehler, sind 14 Bit/s möglich. Die einfache Machbarkeit demonstriert erneut die Gefährlichkeit verdeckter Kanäle auch für Heimanwendungen

Capturing Users’ Privacy Expectations To Design Better Smart Car Applications

Smart cars learn from gathered operating data to add value to the users’ driving experience and increase security. Thereby, not only users benefit from these data- driven services; various actors in the associated ecosystem are able to optimize their business models based on smart car related information. Continuous collection of data can defy users’ privacy expectations, which may lead to reluctant usage or even refusal to accept services offered by smart car providers. This paper investigates users’ privacy expectations using a vignette study, in which participants judge variations of smart car applications, differing with respect to factors such as data transmission and the type of information transferred. We expect to identify application dependent privacy expectations, that eventually yield insights on how to design smart car applications and associated business models that respect users’ privacy expectations