Microcracks and Vortices in Superconducting Thin Films

In this work, superconducting YBa₂ Cu₃O_6+x (YBCO) thin films have been studied with the experimental focus on the anisotropy of BaZrO₃ (BZO) doped YBCOthin films and the theoretical focus on modelling flux pinning by numerically solving Ginzburg- Landau equations. Also, the structural properties of undoped YBCO thin films grown on NdGaO₃ (NGO) and MgO substrates were investigated. The thin film samples were made by pulsed laser ablation on single crystal substrates. The structural properties of the thin films were characterized by X-ray diffraction and atomic force microscope measurements. The superconducting properties were investigated with a magnetometer and also with transport measurements in pulsed magnetic field up to 30 T. Flux pinning was modelled by restricting the value of the order parameter inside the columnar pinning sites and then solving the Ginzburg-Landau equations numerically with the restrictions in place. The computations were done with a parallel code on a supercomputer. The YBCO thin films were seen to develop microcracks when grown on NGO or MgO substrates. The microcrack formation was connected to the structure of the YBCO thin films in both cases. Additionally, the microcracks can be avoided by careful optimization of the deposition parameters and the film thickness. The BZO doping of the YBCO thin films was seen to decrease the effective electron mass anisotropy, which was seen by fitting the Blatter scaling to the angle dependence of the upper critical field. The Ginzburg-Landau simulations were able to reproduce the measured magnetic field dependence of the critical current density for BZO doped and undoped YBCO. The simulations showed that in addition to the large density also the large size of the BZO nanorods is a key factor behind the change in the power law behaviour between BZO doped and undoped YBCO. Additionally, the Ginzburg-Landau equations were solved for type I thin films where giant vortices were seen to appear depending on the film thickness. The simulations predicted that singly quantized vortices are stable in type I films up to quite large thicknesses and that the size of the vortices increases with decreasing film thickness, in a way that is similar to the behaviour of the interaction length of Pearl vortices.

Development and characterization of thin printed films for gas sensing applications

The monitoring and control of hydrogen sulfide (H2S) level is of great interest for a wide range of application areas including food quality control, defense and antiterrorist applications and air quality monitoring e.g. in mines. H2S is a very poisonous and flammable gas. Exposure to low concentrations of H2S can result in eye irritation, a sore throat and cough, shortness of breath, and fluid retention in the lungs. These symptoms usually disappear in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headache, irritability, poor memory, and dizziness. Higher concentrations of 700 - 800 ppm tend to be fatal. H2S has a characteristic smell of rotten egg. However, because of temporary paralysis of olfactory nerves, the smelling capability at concentrations higher than 100 ppm is severely compromised. In addition, volatile H2S is one of the main products during the spoilage of poultry meat in anaerobic conditions. Currently, no commercial H2S sensor is available which can operate under anaerobic conditions and can be easily integrated in the food packaging. This thesis presents a step-wise progress in the development of printed H2S gas sensors. Efforts were made in the formulation, characterization and optimization of functional printable inks and coating pastes based on composites of a polymer and a metal salt as well as a composite of a metal salt and an organic acid. Different processing techniques including inkjet printing, flexographic printing, screen printing and spray coating were utilized in the fabrication of H2S sensors. The dispersions were characterized by measuring turbidity, surface tension, viscosity and particle size. The sensing films were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and an electrical multimeter. Thin and thick printed or coated films were developed for gas sensing applications with the aim of monitoring the H2S concentrations in real life applications. Initially, a H2S gas sensor based on a composite of polyaniline and metal salt was developed. Both aqueous and solvent-based dispersions were developed and characterized. These dispersions were then utilized in the fabrication of roll-to-roll printed H2S gas sensors. However, the humidity background, long term instability and comparatively lower detection limit made these sensors less favourable for real practical applications. To overcome these problems, copper acetate based sensors were developed for H2S gas sensing. Stable inks with excellent printability were developed by tuning the surface tension, viscosity and particle size. This enabled the formation of inkjet-printed high quality copper acetate films with excellent sensitivity towards H2S. Furthermore, these sensors showed negligible humidity effects and improved selectivity, response time, lower limit of detection and coefficient of variation. The lower limit of detection of copper acetate based sensors was further improved to sub-ppm level by incorporation of catalytic gold nano-particles and subsequent plasma treatment of the sensing film. These sensors were further integrated in an inexpensive wirelessly readable RLC-circuit (where R is resistor, L is inductor and C is capacitor). The performance of these sensors towards biogenic H2S produced during the spoilage of poultry meat in the modified atmosphere package was also demonstrated in this thesis. This serves as a proof of concept that these sensors can be utilized in real life applications.

The Role of Structural Imperfections in Sr2FeMoO6 Thin Films

In this work, Sr2FeMoO6 (SFMO) thin films were studied with the main focus on their magnetic and magneto-transport properties. The fabrication process of pulsed laser deposited SFMO films was first optimized. Then the effects of strain, film thickness and substrate were thoroughly investigated. In addition to these external factors, the effect of intrinsic defects on the magnetic properties of SFMO were also clarified. Secondly, the magnetoresistivity mechanims of SFMO films were studied and a semiempirical model of the temperature dependence of resistivity was introduced. The films were grown on single crystal substrates using a ceramic target made with sol-gel method. The structural characterization of the films were carried out with X-ray diffraction, atomic force microscopy, transmission electron microscopy and high kinetic energy photoelectron spectroscopy. The magnetic properties were measured with SQUID magnetometer and the magneto-transport properties by magnetometer with a resistivity option. SFMO films with the best combination of structural and magnetic properties were grown in Ar atmosphere at 1050 °C . Their magnetic properties could not be improved by the ex situ post-annealing treatments aside from the treatments in ultra-high vacuum conditions. The optimal film thickness was found to be around 150 nm and only small improvement in the magnetic properties with decreasing strain was observed. Instead, the magnetic properties were observed to be highly dependent on the choice of the substrate due to the lattice mismatch induced defects, which are best avoided by using the SrTiO3 substrate. The large difference in the Curie temperature and the saturation magnetization between the SFMO thin film and polycrystalline bulk samples was connected to the antisite disorder and oxygen vacancies. Thus, the Curie temperature of SFMO thin films could be improved by increasing the amount of oxygen vacancies for example with ultra-high vacuum treatments or improving the B-site ordering by further optimization of the deposition parameters. The magneto-transport properties of SFMO thin films do not follow any conventional models, but the temperature dependence of resistivity was succesfully described with a model of two spin channel system. Also, evidences that the resistivity-temperature behaviour of SFMO thin films is dominated by the structural defects, which reduce the band gap in the majority spin band were found. Moreover, the magnetic field response of the resistivity in SFMO thin films were found to be superposition of different mechanisms that seems to be related to the structural changes in the film.

Magnetophotoresistance in Pr 1–x CaxMnO3 Thin Films

In this work, a colossal magnetoresistive (CMR) Pr1−xCaxMnO3 (PCMO) man- ganite thin films and polycrystalline samples were studied with the main focus on the properties of the insulator to metal Mott phase transition. The polycrystalline PCMO samples were fabricated with the solid state reaction method. The polycrystalline sam- ples were further processed into the epitaxial thin films with the pulsed laser deposition method (PLD). The structural and magnetic properties of the samples were systemat- ically investigated and the thin films samples were further investigated with magneto- transport measurement where the thin films response to illumination was also studied. After the successful synthesis of polycrystalline PCMO samples with varying x = between 0.0 - 0.5, the magnetic characterization of the samples showed rich magnetic properties having the signatures of the magnetic phase coexistence of antiferromag- netic (AFM) and ferromagnetic (FM) ordering and cluster glass behaviour. With the increased doping concentration from x = 0.3 to 0.5, the AFM charge-order (CO) phase started to form up being strongest on the sample x = 0.5. This AFM CO phase could be melted with the high external magnetic field at temperatures below Neel’s tempera- ture TN inducing an irreversible first order metamagnetic AFM to FM phase transition. The strength of the AFM CO phase decreased with decreasing Ca concentration and increasing temperature. The polycrystalline PCMO samples with Ca concentrations of 0.3 - 0.5, showing metamagnetic behaviour, were selected for the fabrication of the thin film samples. The films were grown using two different in situ oxygen treatment temperatures at 500 ◦C and 700 ◦C in the PLD system. The films with x = 0.4 and 0.5 showed weaker AFM CO phase with greatly reduced melting fields when compared to polycrystalline samples. Also, the robustness of the AFM CO phase was further decreased in thin films with the lower oxygen treatment temperature of 500 ◦C. The magneto-transport measurements made on the thin films showed that the melting of AFM CO phase was connected to CMR effect where the increasing magnetic field induced an insulator to metal phase transition, which reduces the resistivity of the film around nine orders of magnitude. The use of illumination during the magneto-transport measurements showed a vari- ety of intriguing phenomena including magnetophotoresistance. The illumination had a huge effect to the insulator to metal transition (IMT) reducing the transition magnetic field significantly. Moreover, by magnetically biasing the thin films with the constant external magnetic field, the IMT could be induced by switching on the illumination.

Evakkolapsi : ennakkosuunnittelun tuotannollisten ratkaisujen vaikutus dokumentin sisältöön

This thesis contains two parts: documentary Refugee Child (Evakkolapsi) and written thesis. The written thesis screens how pre-productional decisions made by producer and director can influence the content of the documentary. The documentary film is first approached from the historical and theoretical point of view. The documentary Refugee Child is evaluated, especially from the producers point of view. The effect of the productional decisions to the content in the Refugee Child are evaluated. The word documentary film has multiple different meanings and it is beeing used in various contexts. There is numerous opinions about what is the difference between a documentary film and a television documentary. The people in the audiovisual field and the channel networks seem to use the word documentary about very different kinds of films. In order to understand the difficulty of this definition the history of the documentary film and the devicion of Bill Nichols' six modes is shortly viewed. Focusing on the pre-production of documentary is rewarding. There is various altering factors in the production of the documentary. The producer and director should be prepared both technically and substancially.

Menestystarinoilla maailmalle : Music Export Finland musiikkialan yrittäjien tukena kansainvälistymisessä

Opinnäytetyö on kirjallinen selvitys, jossa kartoitetaan musiikkialan ammattilaisten näkemyksiä musiikkialan vientiorganisaatio Music Export Finlandin vienninedistämistyön palveluista. Työn tarkoituksena on selvittää, minkälaiseksi vientityötä jo jonkin aikaa tehneet yrittäjät kokevat ja määrittelevät yhdistyksen roolin sekä sen palveluiden tarpeellisuuden omassa käytännön vientityössään. Teoreettinen viitekehys muodostettiin vientitoiminnan käsikirjoista sekä asiantuntijaorganisaatio Finpron kansainvälistymisstrategian mallista, jonka pohjalta tehtiin myös kuuden asiantuntijan haastattelut. Musex tarjoaa palveluita lähinnä vientitoiminnan käytännön toteutusvaiheeseen. Musexin olemassaolo koetaan alalla yleisesti positiiviseksi asiaksi, vaikka vientityötä jo jonkin aikaa tehneet yrittäjät eivät välttämättä hyödykään yhdistyksen palveluista käytännön tasolla. Musex näyttäytyy heille lähinnä alan yleisen tiedottajan roolissa, musiikkialan yhteisenä äänitorvena, jonka tehtävä on ylläpitää toimivia suhteita valtiovaltaan, lisätä toimialan näkyvyyttä ja edesauttaa toimialan rakenteiden kehittämistä alan intressien mukaisesti. Heille on tärkeää, että musiikkitoimialan tunnettuus ja arvostus lisääntyvät julkisen vallan edustajien joukossa, mitä kautta tarvittavaa rakennemuutosta voidaan viedä konkreettisesti eteenpäin. Musiikkialalla menestyy se, joka hallitsee koko laajan liiketoiminnallisen paketin sekä pystyy tarjoamaan faneilleen jotain ainutlaatuista ja eksklusiivista. Musiikkialan yrityksissä harjoitetaan ammattimaista vientitoimintaa alalle ominaisilla tavoilla ja strategioilla, jotka useinkin poikkeavat monen muun alan menettelytavoista. Vientityön tekeminen edellyttää yrityksiltä halua ja kykyä ajatella liiketoiminnallisesti koko toimintaa, sekä paljon työtä. Yhteistyö koko alan kesken on kansainväliselle toiminnalle ehdotonta. Musiikkitoimialan suurin kompastuskivi yhä edelleen on yleisen arvostuksen ja uskottavuuden puute tai sen vähäisyys, sekä rahoitus. Opinnäytetyö on hankkeistettu sekä Musexin kanssa että Stadian t&k -hankkeeseen Suomalaisten musiikkialan pienyrittäjien vientivalmiuksien kehittäminen.

Reading films through political classics : genres of politics in popular cultures

Abstract: Readin films through political classics