The aim of this project is to study the surface structure of the transition-metal dichalcogenide (TMDC) TaS2 with helium atom scattering. TaS2 has a particularly rich phase diagram involving several charge-density wave (CDW) transitions driven by strong electronic correlations and electron-phonon coupling upon changes of the surface temperature. Helium scattering measurements at different sample temperatures should allow to follow the phase transitions and the changes upon the surface structure / charge density with temperature.
Compensation: € 2640 Contact: tamtoeglnoSpam@tugraz.at
For studies of the adsorption of gas molecules on various material surfaces, so-called Dirac materials, the setup of a gas dosing system is necessary. Therefore, an existing experimental apparatus should be extended with a setup for the dosage of gases. To deliver gas adsorbates onto the surface in a controlled and quantitative way, a gas-handling system with a microcapillary array beam will be designed and constructed. The master student will be responsible for design and setup of the gas dosing system with help provided by our group and should then run first adsorption tests on Dirac material surfaces.
Die Methode der Elektromagnetischen Levitation ermöglicht eine berührungsfreie Bestimmung von thermophysikalischen Eigenschaften metallischer Schmelzen. Dabei werden durch ein inhomogenes elektromagnetisches Hochfrequenzfeld Wirbelströme im Probenmaterial erzeugt, welche aufgrund der ausgeübten Lorentzkraft ein schwebendes Positionieren der Probe ermöglichen und gleichzeitig zu einem Aufheizen des Probenmaterials in die flüssige Phase führen. Die Probentemperatur wird optisch durch pyrometrische Messung bestimmt und gleichzeitig die Probengeometrie mittels zweier High-Speed-Kameras aufgezeichnet. Unter Verwendung dieser Messgrößen wird die Bestimmung von Dichte und Oberflächenspannung der Probe in Abhängigkeit der Temperatur ermöglicht. Es besteht die Möglichkeit an diese Diplomarbeit weiterführend ein Dissertationsprojekt anzuschließen. Kontakt: pottlachernoSpam@tugraz.at
[-] Metal clusters with diameters in the nanometer range show outstanding chemical features which differ significantly from the bulk material. Particularly interesting is the ability to catalyse selected reactions. The aim of this diploma thesis is to study the activity and selectivity of selected materials (Au, Ag, Cu, Pt, Fe, Ni) for the adsorption and follow-up dehydrogenation of short-chained alkanes with density functional theory, starting with the evaluation of basic properties such as adsorption energies and their dependence on particle structure, composition and size.
Compensation: 2640 €Contact: Ass. Prof. Andreas Hauser andreas.hausernoSpam@tugraz.at
[-] The master student will be part of a team working on NN development. He/She will be focusing on the crucial task of writing parsing scripts for the output of the selected program packages and will develop a program which translates cartesian coordinates or z-matrix geometries into so-called symmetry functions, a non-redundant input vector format for the neural network. This technically challenging part will be performed with the help of Dr. Marquetand, an experienced user and developer of NNs for chemistry applications from the University of Vienna, who offered his assistance.
[-] A Master student will join the project listed above in the second half of 2017. After getting introduced to Q-Chem and quantum chemistry methods in general, it will be his task to assist with the parsing of Q-Chem output, to perform a series of benchmark ab initio calculations on small metal clusters to provide first test sets for the training of the NN, and to collaborate with the PhD students on finalizing a first draft version of the NN.
The helium-droplet technique is used to create our `Nano-Mozartkugeln', which are mixed-metallic clusters of Au and Cu with diameters in the nanometer range. The particles are then deposited on supports of amorphous carbon or SiO2. The results are checked by electron microscopy imaging with the help of our colleagues at the FELMI-ZFE. A newly designed reaction chamber has to tested for leaks and for the accessible temperature range given by the built-in sample heater. After that, first BET adsorption measurements of nitrogen gas are planned. Finally, a selection of materials is then placed into the reaction chamber and exposed to a He-diluted mixture of butadiene, propene and hydrogen for a series of temperature-controlled reaction measurements. Gas composition during reaction will be monitored by the quadrupole mass spectrometer attached to the chamber.
Our recent work is geared towards the formation of nanoparticles with core-shell structure: Onion-like particles with shells consisting of different materials. Our group has a long tradition in the preparation of nanoparticles in cold superfluid helium nanodroplets at temperatures of only 0.37 K. We are now looking for a motivated master student in order to push our approach to the next step: Adding an additional layer of molecules between a metal shell and a metal core to form particles known in literature as “quantum matryoshkas”. The special plasmonic properties of these particles, based on localized surface plasmon resonances, can locally cause a strong enhancement of electromagnetic radiation. We are planning to exploit this effect in order to perform Raman spectroscopy on the molecular matryoshka layer in-situ, while still inside the helium droplets, as well as with deposited particles.
Compensation: 2640 EURContact: Florian Lackner florian.lacknernoSpam@tugraz.at
Institut of Experimental Physics Graz University of Technology Petersgasse 16 8010 Graz Austria
schultzenoSpam@tugraz.at wolfgang.ernstnoSpam@tugraz.at pottlachernoSpam@tugraz.at andreas.hausernoSpam@tugraz.at markus.kochnoSpam@tugraz.at tamtoeglnoSpam@tugraz.at bernhardtnoSpam@tugraz.at