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Institut für Festkörperphysik
Advanced process nodes for analog radiation tolerant ICs
Advanced CMOS process nodes like 28 nm and 40 nm have been introduced in commercial products several years ago. Usage of these processes for high performance digital circuits is being continuously and broadly exploited. But their applicability for analog functions of mixed-signal systems is still to be further explored. In particular this is an interesting research are for particle physics experiments, where scaled down MOS transistor features could offer advantages for radiation tolerance, which is a subject of this project.
Contact: Alicja Michalowska-Forsyth (firstname.lastname@example.org)
Modeling and Characterization of Semiconductor Devices at Cryogenic Temperatures
The objective of the master thesis is to investigate the behavior of semiconductor devices (resistors, MOS-transistors) in a CMOS-technology at temperatures below 20K. For this, both, simulations on a device-physics level and measurements of test devices should be performed. The simulations will be done in Synopsis TCAD using the latest models. Their results should clearly show the influence of temperature on electrical device properties like resistance, gain and bandwidth. Since semiconductor performance is usually not modeled in these regimes, advanced physical models can be implemented using a C++ API to account for effects not yet implemented in the software.
Deposition and characterization of coatings by Molecular Layer Deposition
Molecular layer deposition (MLD) has gained attention in the past few years as the method-of-choice to synthesize (ultra-)thin pinhole-free organic/inorganic hybrid films, the so-called ´metalcones´. MLD enables the deposition of such films with atomic level control over growth, due to its self-limiting nature. By post-processing of the metalcone layers, porous metal oxide can be obtained, paving the road for numerous applications, such as photocatalysis, (bio-)sensing, and separation membranes.
 P. Sundberg, M. Karppinen, Beilstein J. Nanotechnol. 2014, 5, 1104.
Start: as soon as possible
Dr. Alberto Perrotta,
Porosimetry set-up and study
Porous materials have many advantages, such as large surface areas and the possibility to be loaded with additional (active) substances. The characterization of porosity and pore size in bulk materials is well-established, and robust theories can be used to determine the voids fraction. However, in order to adopt porous materials in electronic devices (e.g., bio- and gas-sensors) often thin films need to be used. The characterization of the porosity in thin films is not trivial and the conventional methods cannot be applied, because of the limited amount of material present.
Start: as soon as possible
Dr. Alberto Perrotta,
The advent of Machine Learning methods has unlocked great potential in computational studies. In particular the exploration of surface structures, that was previously thought to be completely unfeasible, has surged in the recent years. At the same time, machine learning studies are often criticized for their lack of physical insight.
The solution of crystal structures from thin films is a contemporary problem in crystallography. A combined experimental / theoretical approach is used where the first step is a grazing incidence x-ray diffraction experiment. The diffraction patterns have to be indexed, which requires the assignment of Laue indices to individual Bragg peaks. The result of the indexation procedure is the geometry of the crystallographic unit cell in terms of lattice constants a, b, c, and the angles α , β , γ. For that purpose, a computer code has to be developed which performs an indexation procedure for grazing incidence diffraction pattern.
Goal: Development of atomistically motivated structure-to-property relationships for heat transport in organic semiconductors a property, that is crucial for device operation, but is still largely unexplored such that the suggested studies can have a huge impact.
Inorganic/Organic interfaces are of great relevant to a large variety of applications, ranging from catalysis and corrosion protection to appliances such as large-area OLED-TVs. Of particular interest is the charge-transfer across the interface, which typically governs the overall performance of the system. Depending on the strength of the interaction between substrate and adsorbate, two archetypes for charge-transfer are commonly observed. For strongly interacting, chemisorbed molecules, new bonds are formed and each molecule at the surface becomes fractionally charged. Conversely, if the interaction is weak, i.e. the molecule physisorbs, some molecules acquire an integer electron while others remain neutral.
The molecule HATCN is a strong electron acceptor that is commercially used in OLEDs to modify the property of metal substrates. Adsorbed on silver, this molecule shows unusual, fascinating physics. At low coverage, the molecule forms honeycomb patterns, which can be exploited as epitaxial growth template. When the coverage is increased, however, the first monolayer rearranges. This drastically changes the material properties, in particular the systems work function.
We are currently seeking Master students to work on on the following topics: