Materials Physics - Open positions Diploma Workers

Open positions - Diploma Workers (X-jobb)

We are looking for students to work on the following projects:

1. Simulation and fitting of polarised neutron reflectivity data

The task within this project will be to simulate and fit polarised neutron reflectivity data from EuS/TM multilayers. Recently, strong room temperature magnetisation was observed in EuS/Co multilayers. In a series of neutron scattering experiments we have collected data than can be used to estimate experimentally the extension of the magnetic polarisation in EuS. You will use a specifically developed fitting tool for reflectivity data, called GenX. Resulting data will be combined with input from x-ray circular magnetic dichroism experiments in order to provide more reliable information. This project requires some basic knowledge about computer use and optionally programming.

Contact Vassilios Kapaklis for more information

2. Magnetotransport in amorphous nanoscale films and multilayers

Developing materials and devices where the magnetic and electrical properties are linked is the subject of the relatively new field of spintronics. This project involves studying the electrical transport properties of amorphous magnetic films. Amorphous magnetic films are attractive for spintronic devices due to their high degree of uniformity and potential for tuning of magnetic and electronic properties. Yet, the mechanisms defining their electrical properties are not well understood. The project will involve measurements of resistivity, Hall effect and magnetoresistance in nanoscale films from 10 K up to room temperature. Multilayers of alternating magnetic and non-magnetic layers will also be studied.

Contact Fridrik Magnus for more information

3. Project work: Determination of oxide thickness by contact resistance measurements.

SKB, the Swedish Nuclear Waste and Fuel Management Company, have the task to handle the radioactive waste from the Swedish nuclear power stations. The burned out nuclear fuel will be deposited according to the KBS-3 system, which is based on three barriers: The copper canister with an iron insert, a bentonite clay buffer and a crystalline basement (primarily rock). The copper canister acts as an impermeable barrier, which has to remain intact during at least 100 000 years¹.

In order to assemble the canister a lid and bottom has to be joined to the main body. This is done by a solid state joining technique called Friction Stir Welding (FSW). The technique has proven to provide unsurpassed quality of the welds. However, it has been seen that the quality of the welds are sensitive to oxides and contamination on the joining surfaces. The cleanliness can to some degree be judged by eye but it would be beneficial to have an unbiased, and simple, measurement of the quality of the surfaces to be joined. One way, which we believe could be suitable, is to conduct contact resistance measurement as any contamination on a copper surface will lower its conductance. However, some care must be taken not to penetrate the oxide layers with the contacting probe.

The goal of this project is to develop a measurement technique for contact resistance measurements on copper surfaces in a production environment. Also, calibration procedures to provide an estimate of the oxide thickness would be desirable.

¹For more information see: http://www.skb.se/english

4. Studies of surface structures using light scattering.

This project will involve development of the existing apparatus to use a CCD camera to collect data over a wide angle range simultaneously. Studies will be made on patterned semiconductor substrates. Modern devices require that patterns be created on a range of small length scales. This study will help develop a new technique for characterisation of such materials.

5. X-ray reflection studies of lyotropic liquid crystals

Concentrated solutions of some surfactants in water form liquid crystal phases. There is evidence that some of these will order against planar substrates. The project will involve design of a cell to allow X-ray measurements under controlled atmospheres on an X-ray reflectometer/diffractometer.

6. Magneto optic spectroscopy of advanced materials

This project is focused on the exploration of energy dependent rotation of light from surfaces. The aim is twofold: Establish spectroscopic magneto optical of few elements and secondly to explore how thick a layer has to be to give the signature corresponding to the bulk like response.

7. Quantum and classical diffusion of light interstitials

The diffusion of light interstitials can be described by classical over-barrier jumps at elevated temperatures. At low temperatures, the transport can only been described by using quantum tunnelling. The aim of the project is to address the borders between the classical and quantum regime using isotopes of hydrogen.

8. Liquid particle dynamics

The project work is aimed at understanding how to make novel liquid conductors that are formed of dispersions of particles in liquids. The initial study will will investigate the flow properties (rheology) of particles in oils and how flow and other applied fields alter the structure. Experiments will involve studies with optical microscopes and light scattering. The project will require design of appropriate measuring cells and use of computers to
analyse images. Extension of an existing light scattering apparatus with a CCD camera will be useful for studying anisotropic scattering.

9. Conductivity of dispersed nanoparticles

The project work is aimed at understanding how conductivity of a network of nanoparticles can be manipulated by the use of external fields. The work is based on experimental and theoretical efforts, including calculations of dipolar interactions of magnetic nanoparticles in the nanometer range. The measurements involve four point conductivity measurements in varying magnetic field as well as calculations using the NIST software package OOMMF (see: http://math.nist.gov/oommf/).

10. Elastic properties of extremely thin nano-laminates

The elastic properties of extremely thin layered materials are exceedingly unpredictable. The ductility and other elastic response depends not only on the inherent properties of the constituents, the interface as well as defects play a major role. The goal of the project is to explore the elastic properties of thin amorphous layers, forming a multilayer consisting of a metallic and oxide layer. The constituents will have large difference in the inherent elastic response and by varying both the repeat distance as well as the ratio of the layers, an understanding of the influence of the different contributions to the overall elastic properties will emerge. This project is conducted in a close collaboration with Inficon (industrial partner).

11. Magneto-optic domain observations

The scope of this project is optimization of measurement conditions in a magneto-optical microscope. It comprises experimental work to determine the most suitable conditions (e.g. choice of microscope settings, colour filters, angles of incidence, camera settings) for various magnetic materials, primarily thin films, connected to the current research projects in the group. The work includes basic digital image processing.

12. Polymer melts under deformation:

Polymer melts show unique mechanical properties as they may show liquid or solid behavior depending on the experimental conditions. This manifests e.g. in a non Newtonian behavior, which means that the viscosity is dependent on the applied shear rate. For an entangled polymer solution one may imagine a disentanglement under stress resulting in reduced viscosity. In this project we intend to shear polymer melts versus a layer of the same polymer grafted to the solid interface. Other than expected first results show that the chains do not disentangle but the chemical bonds break.

13. Surface ordering under shear:

In fluid mechanics flow is described by the Navier-Stokes equation in the bulk and a no-slip boundary condition at the solid interface. However, recently, both experiments and theory have shown that on a microscopic scale liquids may undergo significant slip at a solid wall. The magnitude of the slip length and its relation with the relevant surface parameters on which it depends, are presently under intense discussion in the literature and not well understood on the nm length scale. We contribute to this issue by investigation of surface ordering in samples that show correlations on mesoscopic length scales as well as Newtonian liquids mainly by scattering techniques.

14. Characterization of functionalized surfaces:

Surface coatings are of eminent importance for application as well as for fundamental science. One possibility to functionalize surfaces is to cover them with molecules that change the surface energy. Typically the quality and properties of the coating has then to be verified by x-ray reflectometry, ellipsometry and contact angle measurements. This project will involve the development of these techniques and apply them to kinds of surface coatings

15. Frequency dependent conductivity measurements on liquid and solid materials (using lock-in techniques)

This project is focused on the study of conductivity properties of samples being in the liquid or solid state and the dependence of the latter on frequency. Such studies can be a powerful tool in the effort to learn more about the microstructure of materials as well as dissipation mechanisms. The project will involve design and construction of suitable sample cells, as well as setting up the experiment and implementing lock-in amplifier techniques for the signal analysis. Some programming skills of measurement software like Labview will also be developed.

16. Self organization in soft matter

Self organization is present everywhere in Nature and at all lengthscales. In the present project we will focus on the self organization properties of soft materials and try to characterize the emerging structures. Material candidates for this project are nanoparticles and polymers or copolymers. A variety of different techniques like Langmuir-Blodgett film preparation, spin coating etc. exist for the preparation of samples. Characterization will take place using scattering techniques (optical or X-ray), scanning probe microscopy and conductivity measurements.

17. Advanced x-ray reflectivity modelling

Your task will be to develop new methods to analyse x-ray reflectivity and neutron reflectivity data in a more time efficient manner. You will solve the wave equation for different cases and implement them in a open source program that we at material physics maintain. If time permits you can also apply your developed method on real data. This project requires knowledge in programming.

18. Simulation and optimization of a neutron reflectometer

We, at material physics, are partly responsible for a neutron reflectometer at Institute Laue-Langevin in Grenoble, France. The instrument is used to study the structure of many different thin-film materials such as polymers and soft matter films as well as hydrogen uptake and magnetic moments in various materials. The aim of this project is two-fold. Firstly, the theoretical performance of the current instrument need to be simulated and compared to the measured specifications. Secondly, as a large part of the facility is being reconstructed and there are new possibilities to enhance the performance of the instrument in the future. Therefore we require help to simulate new incarnations of the instrument and optimize the performance given the boundary conditions set by external factors. This require some knowledge of programming and good analytical skills. The project involves travels and stays at the instrument in Grenoble, France.

19. X-ray scattering studies of nanolaminates

The use of x-ray diffraction can yield a detailed understanding of the structural properties of multilayers and thin film. This is of paramount importance for understanding the function of materials. in this project you do a structural analysis of a system using x-ray diffraction and x-ray reflectivity to determine interface sharpness and detailed strain profile. This work combines experimental work and computer aided refinements. If time permits additional functional characterizations can be conducted that can be related to the structure.

All these projects are suitable for experimentalists with an interest in instrumentation. The work is planned for 30 ECTS credits but shorter projects could be discussed.

Please contact Björgvin Hjörvarsson (bjorgvin.hjorvarsson@fysik.uu.se or 018 471 3837) or Adrian Rennie (Adrian.Rennie@fysik.uu.se or 018 471 3596) about these projects or to discuss other work in the group.

All the senior members of the group are pleased to discuss project work in materials physics. A range of other projects may be available in the various areas of research.