Development of silicon based electronics have revolutionized our every day life during the last three decades. Nowadays Si based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, Si cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for a progress in state of the art electronics. Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in the current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene. III-group nitrides have been extensively studied and already have proven their high efficiency as light sources for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for III-group nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions. Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical contact within the structure. Moreover, the use of electrical contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures. The optical Hall effect is an external magnetic field induced optical anisotropy in  conductive layers due to the motion of the free charge carriers under the influence of the Lorentz force, and is equivalent to the electrical Hall effect at optical frequencies. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. In principle, a single optical Hall effect measurement can provide quantitative information about free charge carrier types, concentrations, mobilities and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. Further, it was demonstrated that for transparent samples, a backside cavity can be employed to enhance the optical Hall effect. Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric data by varying physically significant parameters. Analysis of the optical response of samples, containing free charge carriers, employing optical models based on the classical Drude model, which is augmented with an external magnetic field contribution, provide access to the free charge carrier properties. The main research results of the graduate studies presented in this licentiate thesis are summarized in the five scientific papers. Paper I. Description of the custom-built terahertz frequency-domain spectroscopic ellipsometer at Linköping University. The terahertz ellipsometer capabilities are demonstrated by an accurate determination of the isotropic and anisotropic refractive indices of silicon and m-plane sapphire, respectively. Further, terahertz optical Hall effect measurements of an AlGaN/GaN high electron mobility structures were employed to extract the two-dimensional electron gas sheet density, mobility and effective mass parameters. Last, in-situ optical Hall effect measurement on epitaxial graphene in a gas cell with controllable environment, were used to study the effects of environmental doping on the mobility and carrier concentration. Paper II. Presents terahertz cavity-enhanced optical Hall measurements of the monolayer and multilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm−2 range and a carrier mobility of 1550 cm2/V·s. For the multilayer epitaxial graphene, n-type doping with a carrier density in the low 1013 cm−2 range, a mobility of 470 cm2/V·s and an effective mass of (0.14 ± 0.03) m0 were extracted. The measurements demonstrate that cavity-enhanced optical Hall effect measurements can be applied to study electronic properties of two-dimensional materials. Paper III. Terahertz cavity-enhanced optical Hall effect measurements are employed to study anisotropic transport in as-grown monolayer, quasi free-standing monolayer and quasi free-standing bilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed a strong anisotropy in the carrier mobilities of the quasi freestanding bilayer graphene. The anisotropy is demonstrated to be induced by carriers scattering at the step edges of the SiC, by showing that the mobility is higher along the step than across them. The scattering mechanism is discussed based on the results of the optical Hall effect, low-energy electron microscopy, low-energy electron diffraction and Raman measurements. Paper IV. Mid-infrared spectroscopic ellipsometry and mid-infrared optical Hall effect measurements are employed to determine the electron effective mass in an In0.33Ga0.67N epitaxial layer. The data analysis reveals slightly anisotropic effective mass and carrier mobility parameters together with the optical phonon frequencies and broadenings. Paper V. Terahertz cavity-enhanced optical Hall measurements are employed to study the free charge carrier properties in a set of AlGaN/GaN high electron mobility structures with modified interfaces. The results show that the interface structure has a significant effect on the free charge carrier mobility and that the sample with a sharp interface between an AlGaN barrier and a GaN buffer layers exhibits a record mobility of 2332±73 cm2/V·s. The determined effective mass parameters showed an increase compared to the GaN value, that is attributed the the penetration of the electron wavefunction into the AlGaN barrier layer.

In a strongly correlated material the localized electrons, typically the electrons in the 3d-orbitals, become entangled with each other through the Coulomb interaction. However, these electrons also interact with more mobile (itinerant) electrons in the s- and p-orbitals. The latter process called screening as it effectively reduces the strength of the interaction between the 3d-electrons. A less studied and often neglected effect of the screening is that it also entangles the 3d-electrons with the itinerant electrons, which is equivalent to a leakage of quantum information from the 3delectrons to the environment. This process leads to decoherence since it causes the 3d-electrons to effectively lose some of their quantum mechanical properties. But what does this mean for our understanding of strongly correlated materials and can this decoherence effect be of such magnitude that neglecting it may qualitatively affect the calculated material properties? This is the question this report tries to answer, but for a minimal impurity model consisting of an atom and a few surrounding bath orbitals. / I korrelerade atomer kan lokaliserade elektroner, som elektroner i 3d orbitaler, bli kvantmekaniskt sammanflätade med varandra genom coulomb-växelverkan. Dessa elektroner kan även växelverka med mer mobila elektroner, som elektroner i s- och p-orbitaler. Denna process kallas för skärmning eftersom den effektivt sätt reducerar styrkan på repulsionen mellan elektronerna i 3d-orbitalerna. En mindre känd och ofta ignorerad effekt från skärmningen är att elektronerna i 3d-orbitalerna blir kvantmekaniskt sammanflätade med de mobila elektronerna på ett irreversibelt sätt. Detta är ekvivalent med att information om d-elektronernas position läcker ut till omgivningen. Denna informationsläcka kallas för dekoherens eftersom den ledertill att d-elektronerna förlorar en del av sina kvantmekaniska egenskaper. Frågan blir således vad dekoherens kan ha för betydelse för starkt korrelerade materials egenskaper. Kan denna effekt vara av sådan magnitud att det ger oss en helt felaktig bild om den negligeras? Detta är vad denna rapport syftar till att svara på.

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The matching of a tournament could be a tedious task, especially if there are many teams takingpart. To combat this difficult task this thesis evaluates if, by creating a method, there is a wayto automate this matching. The method proposed is based on only two parameters, shortestdistance and whether the teams have faced each other already. By being based on shortestdistance the method could not only shorten the planning time but also shorten the distance thatthe participants have to travel.To test the proposed method and validate whether it would give a sufficiently good matching itis applied to an already played Bridge tournament. The tournament was played in 2019 andincluded 365 teams and 7 rounds. This tournament was matched manually based partly ondistance and whether the teams have faced each other. Teams were split into clusters andrandomly matched each other within those. Thus, the teams did not often play against the closestteam but never a team very far away. Results are given in the form of maps for each round anda table which compares the distances for both the methods.The method was applied successfully, and each round was, as excepted, a shorter distance thanthe original matching. Thus, proving that an automatic tournament matching can be done. Thereare some improvement and alteration that can be done in the future to find a matching that morelifelike.

In this project a qutrit tripod system is studied to implement quantum gates using non-Abelian geometric phases, allowing for holonomic quantum computation which in turn results in more robust computations. First, a general foundation of the theory is presented. This includes the relevant theory of matrices in Hilbert space, as well as theory of the quantum mechanics used in the report. The method is then described in depth, showing how the pulse area is fixed. Using properties of the Hamiltonian as well as the time-evolution operator of the tripod system the computational subspace can be derived. These findings are combined to show how the computational subspace evolves in time, resulting in the unitary matrix used to form quantum gates. Using educated guesses to find the necessary parameters or utilizing iterative methods to find the parameters are the two main approaches used for constructing the considered gates. Three of the suggested quantum gates are successfully implemented through educated guesses, namely X, T and Z using an angle parametrization of the phase and amplitude of the pulses. The last desired gate is the Hadamard-gate, but the implementation of said gate required numerical approximation. The reasons as to why this is the case, are later discussed.

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The path integral formulation of quantum mechanics generalizes the action principle of classical mechanics. The Feynman path integral is, roughly speaking, a sum over all possible paths that a particle can take between fixed endpoints, where each path contributes to the sum by a phase factor involving the action for the path. The resulting sum gives the probability amplitude of propagation between the two endpoints, a quantity called the propagator. Solutions of the Feynman path integral formula exist, however, only for a small number of simple systems, and modifications need to be made when dealing with more complicated systems involving singular potentials, including the Coulomb potential. We derive a generalized path integral formula, that can be used in these cases, for a quantity called the pseudo-propagator from which we obtain the fixed-energy amplitude, related to the propagator by a Fourier transform. The new path integral formula is then successfully solved for the Hydrogen atom in two and three dimensions, and we obtain integral representations for the fixed-energy amplitude. / Vägintegral-formuleringen av kvantmekanik generaliserar minsta-verkanprincipen från klassisk mekanik. Feynmans vägintegral kan ses som en summa över alla möjliga vägar en partikel kan ta mellan två givna ändpunkter A och B, där varje väg bidrar till summan med en fasfaktor innehållande den klassiska verkan för vägen. Den resulterande summan ger propagatorn, sannolikhetsamplituden att partikeln går från A till B. Feynmans vägintegral är dock bara lösbar för ett fåtal simpla system, och modifikationer behöver göras när det gäller mer komplexa system vars potentialer innehåller singulariteter, såsom Coulomb--potentialen. Vi härleder en generaliserad vägintegral-formel som kan användas i dessa fall, för en pseudo-propagator, från vilken vi erhåller fix-energi-amplituden som är relaterad till propagatorn via en Fourier-transform. Den nya vägintegral-formeln löses sedan med framgång för väteatomen i två och tre dimensioner, och vi erhåller integral-representationer för fix-energi-amplituden.

The research addresses two groups of reactions: chlorine atom reactions with fluorinated propenes and methyl amines. Most of the reactions were studied over a range of temperature and pressure with the goals of (i) assessing the potential importance of the reactions in atmospheric chemistry and (ii) obtaining kinetic and thermochemical information of fundamental physical–chemical interest. In the studies reported herein, laser flash photolysis (LFP) was coupled with time resolved atomic resonance fluorescence (RF) spectroscopic detection of chlorine atoms to investigate chlorine atom kinetics.

A new materials system of a single layered Co(W) barrier/liner coupled with a Cu(Mn) alloy seed was investigated. Atom probe tomography visualized the sub-nanoscale structure of Cu(Mn)/Co(W) system, and thereby revealed Cu diffusion behavior of Co(W). Grain boundaries of Co were found to be the diffusion path, and successfully stuffed by W. Mn in Cu(Mn) also segregated to stuff the grain boundaries of Co. Combination of these two additives enabled high barrier property against Cu diffusion of Cu(Mn)/Co(W). Foreseeing tiny and high-aspect-ratio Cu interconnect features, Cu(Mn)/Co(W) was fabricated by ALD/CVD processes. To maximize the performance, minor impurities of the film incorporated from the ligand of the precursors were controlled by precursor selection. Thin, conformal, and smooth films were finally demonstrated onto a trench substrate.

This study is a systematic literature review on the role of models and representations in the teaching, learning and understanding of the atom and atomic concepts. The aim of the study is to investigate the role of different visual representations, what models and representations are used in the science classroom, how learners interpret different external representations of the atom, what mental models students construct, and how the representations can be used and designed for meaningful learning and teaching of the atom and atomic concepts.   In this systematic literature review, a combination of different databases was used to search for literature, namely ERIC, Scopus and Google Scholar. Some limiters were used to narrow down the returned results: the articles should be peer-reviewed and be published 1990-01-01 or later. Ten of the returned articles were included for individual analysis in the study.   The results of the study show that students often find concepts of atomic structure difficult and confusing. The abstract microscopic world of atoms cannot be seen with the naked eye, and models are therefore necessary and crucial educational tools for teaching atomic concepts in school. However, when using a model, it is important for the teacher to explain the rules of the model, and the advantages and limitations of the representation must be discussed. Analysis of the included articles revealed three types of representations used to represent atomic phenomena: two-dimensional static diagrams or pictures (e.g. a picture of the atom), three-dimensional videos or simulations (e.g. virtual reality simulations), and visual analogies (e.g. the Bohr planetary model of the atom). The use of simulations and interactive learning environments seem to have a positive effect on students’ learning. One of the studies, described in the articles included for analysis, showed that students appreciated the use of virtual reality simulations, since it made abstract concepts easier to understand when they could be visualized.