Inst. Festkörperphysik

192 Items

Recent Submissions
Prozessierung und Anwendung SiO2 basierter Lichtleiter für die optische UVC-Gassensorik

Elmlinger, Philipp Simon (2019)

Diese Arbeit behandelt die Prozessierung verlustarmer Lichtwellenleiter für einen optischen UVC-Gassensor. Durch optische Simulationen wurde zunächst ein geeignetes Material (amorphes Quarzglas) und Design abgeleitet. Mittels Belichtung mit einem Ultrakurzpulslaser und anschließendem selektiven Nassätzen wurden die Lichtleiter aus dem Wafer strukturiert. Die resultierenden rauen Seitenwände füh...

A Miniaturized UV-LED Based Optical Gas Sensor Utilizing Silica Waveguides for the Measurement of Nitrogen Dioxide and Sulphur Dioxide

Elmlinger, Philipp ; Schreivogel, Martin ; Weida, Simon ; Kneissl, Michael (2017-08-15)

Continuing advances in the development of light-emitting diodes (LEDs) in the deep ultraviolet spectral range (DUV) enable miniaturized, mobile, and cost-effective DUV gas sensors. Efficient light coupling, guiding, and splitting plays a key role for stable sensor systems and is realized by lowloss silica based waveguides, fabricated by ultrashort pulsed laser etching and laser polishing. The t...

Spin-ARPES EUV Beamline for Ultrafast Materials Research and Development

Nie, Zhonghui ; Turcu, Ion Cristian Edmond ; Li, Yao ; Zhang, Xiaoqian ; He, Liang ; Tu, Jian ; Ni, Zhiqiang ; Xu, Huangfeng ; Chen, Yequan ; Ruan, Xuezhong ; Frassetto, Fabio ; Miotti, Paolo ; Fabris, Nicola ; Poletto, Luca ; Wu, Jing ; Lu, Qiangsheng ; Liu, Chang ; Kampen, Thorsten ; Zhai, Ya ; Liu, Wenqing ; Cacho, Cephise ; Wang, Xuefeng ; Wang, Fengqiu ; Shi, Yi ; Zhang, Rong ; Xu, Yongbing (2019-01-22)

A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the “Ultrafast Spintronic Materials Facility”, dedicated to engineering ultrafast materials. This facility provides a fast and in-sit...

Effect of Electron Blocking Layer Doping and Composition on the Performance of 310 nm Light Emitting Diodes

Kolbe, Tim ; Knauer, Arne ; Rass, Jens ; Cho, Hyun ; Hagedorn, Sylvia ; Einfeldt, Sven ; Kneissl, Michael ; Weyers, Markus (2017-12-06)

The effects of composition and p-doping profile of the AlGaN:Mg electron blocking layer (EBL) in 310 nm ultraviolet B (UV-B) light emitting diodes (LEDs) have been investigated. The carrier injection and internal quantum efficiency of the LEDs were simulated and compared to electroluminescence measurements. The light output power depends strongly on the temporal biscyclopentadienylmagnesium (Cp...

Structural characteristics of InGaAs/GaP quantum dots and related materials on the atomic scale

Prohl, Christopher (2019)

Self-assembled (In,Ga)As quantum dots (QDs) embedded in a GaP matrix are a promising semiconductor material for possible applications in optoelectronics and nanomemory cells. Even more, GaP with its particular low lattice mismatch to silicon offers the possibility to monolithically integrate III-V semiconductor nanotechnology into silicon. In this thesis, cross-sectional scanning tunneling mic...

Electronic and phononic states of quantum structures

Westerkamp, Steffen (2019)

Colloidal core-shell semiconductor quantum dots present a fascinating field in both semiconductor research and applications, because they share many properties with more conventional quantum dots embedded in bulk semiconductor materials, such as quantum dots produced via a Stranski-Krastanov process. Yet they are are both much simpler to produce, being the product of chemical synthesis methods,...

Deterministically fabricated, quantum dot based single-photon sources for quantum information technologies

Fischbach, Sarah (2019)

First experimental demonstrations proved the potential of quantum information technologies, which in many cases choose the polarization characteristics of single photons to process and transport quantum states. The security of such systems crucially relies on the availability of on-demand single-photon sources. Semiconductor quantum dots demonstrate to be excellent sources of quantum light, whi...

Small-Signal Analysis of High-Performance VCSELs

Hamad, Wissam ; Sanayeh, Marwan Bou ; Siepelmeyer, Tobias ; Hamad, Hassan ; Hofmann, Werner H. E. (2019-02-26)

In this paper, a comprehensive model to describe the small-signal modulation response of ultra-high performance single- and multi-mode vertical-cavity surface-emitting lasers (VCSELs), with modulation bandwidths exceeding 30 GHz, is presented. Traditionally, utmost simplified dynamic models are used to extract dynamic figures of merit from single-mode edge-emitting lasers. These methods are lat...

SEIRA optofluidics of sub-monolayers of biomolecules in nL-volumes

Kratz, Christoph Andreas (2019)

Optofluidics enables one to analyze minute amount of samples and facilitates new ways in the analysis of biological samples which are often only available in small amounts and should be used as economically as possible. The integration of in situ IR spectroscopy for the detection in optofluidics however is in a very early stage. In particular integration of SEIRA spectroscopy with metal island ...

Phononen-assistierte Anregungsprozesse und Hochanregungseffekte in positionierten einzelnen Quantenpunkten

Hitzemann, Ole (2019)

Mit steigender Leistung moderner Rechner und der möglichen Entwicklung verbesserter Algorithmen sowie neuer Technologien wie dem Quantencomputer sind herkömmliche Kryptographieverfahren langfristig nicht mehr sicher. Abhilfe könnte die Quantenkommunikation schaffen, die physikalisch nachweisbar mathematisch sichere Schlüssel übertragen kann. Um nachweislich abhörsicher und mit hoher Effizienz Q...

Eigenschaften ultradünner Galliumnitrid- und -Oxidschichten über InGaN-Quantenfilmen für sensorische Anwendungen

Alamé, Sabine Hildegard Vera (2019)

Die technologische Entwicklung der heutigen Zeit befasst sich zunehmend mit der Kombination traditionell verwendeter Materialien mit organischen Verbindungen. Dadurch ergeben sich eine Vielzahl neuer Anwendungsgebiete und oft einfachere und kostengünstige Bauelemente. In dieser Arbeit wurde untersucht, wie sich das bereits in der Halbleitertechnologie weit verbreitete Materialsystem InGaN und...

Atomic structure and electronic properties of Tb silicide nanowires

Appelfeller, Stephan (2018)

Metallic nanowires grown by self-organisation on Si surfaces may be interesting for future applications in Si based nanotechnology, but they will also show unique physical phenomena, e.g. Peierls transitions or Tomonaga-Luttinger liquid behaviour, if they are characterised by a one-dimensional electronic structure. This thesis concentrates on the physical properties of Tb silicide nanowires, wh...

Influence of a TESb flush on InAs/GaAs submonolayer stacks

Quandt, Paul David Maximilian (2018)

The so-called submonolayer growth mode poses an alternative to the conventional Stranski-Krastanov growth for the fabrication of high densities of quantum dots. Previous investigations, however, showed only weak confinement properties of these submonolayer stacks. The incorporation of Sb provides the possibility to intentionally tune the confinement properties. In this work a MOCVD process was...

Well-ordered iron oxide and sulfide thin films

Davis, Earl Matthew (2018)

In this thesis, the growth of iron oxide and iron sulfide thin films has been investigated. These are materials that are abundantly found in the earth's crust and have long been studied by humanity, having a wide range of properties that have seen their use in many applications. Among these applications, iron oxides have played an important role in catalytic processes such as the Haber-Bosch p...

Electronic and vibrational properties of diamondoid derivatives, graphite, and carbon nanotubes

Tyborski, Christoph (2018)

In this work, we present an analysis of vibrational and electronic properties of diamondoids, graphene, multilayer graphene, graphite, and carbon nanotubes. The realized studies are based on optical spectroscopy, such as Raman spectroscopy, photo luminescence, photo luminescence excitation, and absorption spectroscopy, but also on in-depth model calculations. Although the analyzed material syst...

Optical gain and modal loss in AlGaN based deep UV lasers

Martens, Martin Georg Rudolf (2018)

Because of its direct bandgap covering the ultraviolet (UV) spectral region from 360 nm to 200 nm, the AlGaN material system is a promising candidate for the realization of deep UV laser diodes emitting below 300 nm, being an alternative for bulky and energy consuming excimer or frequency multiplied lasers. Possible applications cover e.g. medical detection, gas sensing, material processing, ...

Phonons and excitons in colloidal CdSe/CdS quantum dots with wurtzite and zincblende crystal structure

Biermann, Amelie Laura (2018)

This thesis presents a thorough analysis of the optical and vibrational properties of colloidal II-VI-semiconductor quantum dots, focussing on the effects of crystal structure differences and the interplay within core-shell QDs on the lattice vibrations, temperature dependent lattice parameters the exciton-phonon coupling and the exciton ne structure. Here, spherical CdSe/CdS QDs of di erent s...

Coherent spectroscopy of InGaAs quantum dots

Strauß, Stefan Maximilian (2018)

Excitons in quantum dots represent a remarkably good two-level system with a large optical dipole transition moment. Although most research currently focuses on enhancing their already outstanding properties as single photon emitters they become also increasingly interesting for experimental fundamental research due to their large dipole transition moment. This thesis presents studies which exp...

Entwicklung einer autark operierenden Plug-and-Play-Einzelphotonenemittereinheit

Schlehahn, Alexander (2018)

Durch die stetige Entwicklung von Anwendungsmöglichkeiten der Quantentechnologie steigt auch die Nachfrage nach effizienten und qualitativ hochwertigen Quellen einzelner Photonen, welche den Grundstein vieler dieser praktischen Konzepte bilden. Daher wird im Rahmen dieser Arbeit die Entwicklung einer kältemittelunabhängigen, fasergekoppelten Einzelphotonenemittereinheit, basierend auf InGaAs-Qu...

Polarization multiplexed photonic integrated circuits for 100 Gbit/s and beyond

Baier, Moritz Friedrich (2018)

In this thesis, a fully integrated dual-polarization (DP) optical transmitter is proposed, developed and demonstrated. The transmitter proposed in this work consists of two key building blocks: a polarization rotator (PR) and two electro-absorption modulators (EAM), laid out in a serial configuration. Furthermore, a laser source is monolithically integrated. All devices are realized in the semi...