Atomic Layer Deposition of Multicomponent Oxide Materials

Atomic layer deposition (ALD) is a method for thin film deposition which has been extensively studied for binary oxide thin film growth. Studies on multicomponent oxide growth by ALD remain relatively few owing to the increased number of factors that come into play when more than one metal is employed. More metal precursors are required, and the surface may change significantly during successive stages of the growth. Multicomponent oxide thin films can be prepared in a well-controlled way as long as the same principle that makes binary oxide ALD work so well is followed for each constituent element: in short, the film growth has to be self-limiting. ALD of various multicomponent oxides was studied. SrTiO3, BaTiO3, Ba(1-x)SrxTiO3 (BST), SrTa2O6, Bi4Ti3O12, BiTaO4 and SrBi2Ta2O9 (SBT) thin films were prepared, many of them for the first time by ALD. Chemistries of the binary oxides are shown to influence the processing of their multicomponent counterparts. The compatibility of precursor volatilities, thermal stabilities and reactivities is essential for multicomponent oxide ALD, but it should be noted that the main reactive species, the growing film itself, must also be compatible with self-limiting growth chemistry. In the cases of BaO and Bi2O3 the growth of the binary oxide was very difficult, but the presence of Ti or Ta in the growing film made self-limiting growth possible. The application of the deposited films as dielectric and ferroelectric materials was studied. Post-deposition annealing treatments in different atmospheres were used to achieve the desired crystalline phase or, more generally, to improve electrical properties. Electrode materials strongly influenced the leakage current densities in the prepared metal insulator metal (MIM) capacitors. Film permittivities above 100 and leakage current densities below 110-7 A/cm2 were achieved with several of the materials.

Cellulose Derivatives : Synthesis, Properties and Applications

Even though cellulose is the most abundant polymer on Earth, its utilisation has some limitations regarding its efficient use in the production of bio-based materials. It is quite clear from statistics that only a relatively small fraction of cellulose is used for the production of commodity materials and chemicals. This fact was the driving force in our research into understanding, designing, synthesising and finding new alternative applications for this well-known but underused biomaterial. This thesis focuses on the developing advanced materials and products from cellulose by using novel approaches. The aim of this study was to investigate and explore the versatility of cellulose as a starting material for the synthesis of cellulose-based materials, to introduce new synthetic methods for cellulose modification, and to widen the already existing synthetic approaches. Due to the insolubility of cellulose in organic solvents and in water, ionic liquids were applied extensively as the reaction media in the modification reactions. Cellulose derivatives were designed and fine-tuned to obtain desired properties. This was done by altering the inherent hydrogen bond network by introducing different substituents. These substituents either prevented spontaneous formation of hydrogen bonding completely or created new interactions between the cellulose chains. This enabled spontaneous self-assembly leading to supramolecular structures. It was also demonstrated that the material properties of cellulose can be modified even those molecules with a low degree of substitution when highly hydrophobic films and aerogels were prepared from fatty acid derivatives of nanocellulose. Development towards advanced cellulose-based materials was demostrated by synthesising chlorophyllcellulose derivatives that showed potential in photocurrent generation systems. In addition, liquid crystalline cellulose derivatives prepared in this study, showed to function as UV-absorbers in paper.

Host Rock Classification (HRC) system for nuclear waste disposal in crystalline bedrock

A new rock mass classification scheme, the Host Rock Classification system (HRC-system) has been developed for evaluating the suitability of volumes of rock mass for the disposal of high-level nuclear waste in Precambrian crystalline bedrock. To support the development of the system, the requirements of host rock to be used for disposal have been studied in detail and the significance of the various rock mass properties have been examined. The HRC-system considers both the long-term safety of the repository and the constructability in the rock mass. The system is specific to the KBS-3V disposal concept and can be used only at sites that have been evaluated to be suitable at the site scale. By using the HRC-system, it is possible to identify potentially suitable volumes within the site at several different scales (repository, tunnel and canister scales). The selection of the classification parameters to be included in the HRC-system is based on an extensive study on the rock mass properties and their various influences on the long-term safety, the constructability and the layout and location of the repository. The parameters proposed for the classification at the repository scale include fracture zones, strength/stress ratio, hydraulic conductivity and the Groundwater Chemistry Index. The parameters proposed for the classification at the tunnel scale include hydraulic conductivity, Q´ and fracture zones and the parameters proposed for the classification at the canister scale include hydraulic conductivity, Q´, fracture zones, fracture width (aperture + filling) and fracture trace length. The parameter values will be used to determine the suitability classes for the volumes of rock to be classified. The HRC-system includes four suitability classes at the repository and tunnel scales and three suitability classes at the canister scale and the classification process is linked to several important decisions regarding the location and acceptability of many components of the repository at all three scales. The HRC-system is, thereby, one possible design tool that aids in locating the different repository components into volumes of host rock that are more suitable than others and that are considered to fulfil the fundamental requirements set for the repository host rock. The generic HRC-system, which is the main result of this work, is also adjusted to the site-specific properties of the Olkiluoto site in Finland and the classification procedure is demonstrated by a test classification using data from Olkiluoto. Keywords: host rock, classification, HRC-system, nuclear waste disposal, long-term safety, constructability, KBS-3V, crystalline bedrock, Olkiluoto

Growth and Modification of Cluster-Assembled Thin Films

Thin film applications have become increasingly important in our search for multifunctional and economically viable technological solutions of the future. Thin film coatings can be used for a multitude of purposes, ranging from a basic enhancement of aesthetic attributes to the addition of a complex surface functionality. Anything from electronic or optical properties, to an increased catalytic or biological activity, can be added or enhanced by the deposition of a thin film, with a thickness of only a few atomic layers at the best, on an already existing surface. Thin films offer both a means of saving in materials and the possibility for improving properties without a critical enlargement of devices. Nanocluster deposition is a promising new method for the growth of structured thin films. Nanoclusters are small aggregates of atoms or molecules, ranging in sizes from only a few nanometers up to several hundreds of nanometers in diameter. Due to their large surface to volume ratio, and the confinement of atoms and electrons in all three dimensions, nanoclusters exhibit a wide variety of exotic properties that differ notably from those of both single atoms and bulk materials. Nanoclusters are a completely new type of building block for thin film deposition. As preformed entities, clusters provide a new means of tailoring the properties of thin films before their growth, simply by changing the size or composition of the clusters that are to be deposited. Contrary to contemporary methods of thin film growth, which mainly rely on the deposition of single atoms, cluster deposition also allows for a more precise assembly of thin films, as the configuration of single atoms with respect to each other is already predetermined in clusters. Nanocluster deposition offers a possibility for the coating of virtually any material with a nanostructured thin film, and therein the enhancement of already existing physical or chemical properties, or the addition of some exciting new feature. A clearer understanding of cluster-surface interactions, and the growth of thin films by cluster deposition, must, however, be achieved, if clusters are to be successfully used in thin film technologies. Using a combination of experimental techniques and molecular dynamics simulations, both the deposition of nanoclusters, and the growth and modification of cluster-assembled thin films, are studied in this thesis. Emphasis is laid on an understanding of the interaction between metal clusters and surfaces, and therein the behaviour of these clusters during deposition and thin film growth. The behaviour of single metal clusters, as they impact on clean metal surfaces, is analysed in detail, from which it is shown that there exists a cluster size and deposition energy dependent limit, below which epitaxial alignment occurs. If larger clusters are deposited at low energies, or cluster-surface interactions are weaker, non-epitaxial deposition will take place, resulting in the formation of nanocrystalline structures. The effect of cluster size and deposition energy on the morphology of cluster-assembled thin films is also determined, from which it is shown that nanocrystalline cluster-assembled films will be porous. Modification of these thin films, with the purpose of enhancing their mechanical properties and durability, without destroying their nanostructure, is presented. Irradiation with heavy ions is introduced as a feasible method for increasing the density, and therein the mechanical stability, of cluster-assembled thin films, without critically destroying their nanocrystalline properties. The results of this thesis demonstrate that nanocluster deposition is a suitable technique for the growth of nanostructured thin films. The interactions between nanoclusters and their supporting surfaces must, however, be carefully considered, if a controlled growth of cluster-assembled thin films, with precisely tailored properties, is to be achieved.

Characterization of hydrophobin proteins at interfaces and in solutions using x rays

Hydrophobins are a group of particularly surface active proteins. The surface activity is demonstrated in the ready adsorption of hydrophobins to hydrophobic/hydrophilic interfaces such as the air/water interface. Adsorbed hydrophobins self-assemble into ordered films, lower the surface tension of water, and stabilize air bubbles and foams. Hydrophobin proteins originate from filamentous fungi. In the fungi the adsorbed hydrophobin films enable the growth of fungal aerial structures, form protective coatings and mediate the attachment of fungi to solid surfaces. This thesis focuses on hydrophobins HFBI, HFBII, and HFBIII from a rot fungus Trichoderma reesei. The self-assembled hydrophobin films were studied both at the air/water interface and on a solid substrate. In particular, using grazing-incidence x-ray diffraction and reflectivity, it was possible to characterize the hydrophobin films directly at the air/water interface. The in situ experiments yielded information on the arrangement of the protein molecules in the films. All the T. reesei hydrophobins were shown to self-assemble into highly crystalline, hexagonally ordered rafts. The thicknesses of these two-dimensional protein crystals were below 30 Å. Similar films were also obtained on silicon substrates. The adsorption of the proteins is likely to be driven by the hydrophobic effect, but the self-assembly into ordered films involves also specific protein-protein interactions. The protein-protein interactions lead to differences in the arrangement of the molecules in the HFBI, HFBII, and HFBIII protein films, as seen in the grazing-incidence x-ray diffraction data. The protein-protein interactions were further probed in solution using small-angle x-ray scattering. Both HFBI and HFBII were shown to form mainly tetramers in aqueous solution. By modifying the solution conditions and thereby the interactions, it was shown that the association was due to the hydrophobic effect. The stable tetrameric assemblies could tolerate heating and changes in pH. The stability of the structure facilitates the persistence of these secreted proteins in the soil.

Formale Aspekte dreier finnischsprachiger Untertitelungsversionen des Films Das Leben der Anderen und bei den Untertitelungen angewandte Übersetzungsstrategien

Työssä tutkitaan yhtäältä saksankielisen elokuvan Muiden elämä ( Das Leben der Anderen ) kolmen suomenkielisen tekstitysversion tekstityksen muotoseikkoja, kuten välimerkkien käyttöä, repliikki- ja rivijakoa, ja toisaalta tekstityksen sisältöseikkoja, joita tarkastellaan tekstityksessä käytettävien käännösstrategioiden avulla. Tutkielmassa tarkastellaan, ovatko tekstityksissä käytetyt muotoseikat konventioiden mukaisia ja minkälaisia käännösstrategioita tekstityksissä on käytetty sekä johtaako tietyn käännösstrategian käyttö merkityksen muutoksiin ja kaventumisiin tekstityksessä. Tutkielman aineistona on elokuva Muiden elämä ja sen kolme suomenkielistä tekstitystä: elokuvateattereissa esitetty versio, DVD-tekstitys ja televisiossa esitetty versio. Hypoteesina oli, että kaikkien versioiden muotoseikat ovat konventioiden mukaisia ja että versioilla on eroavuuksia ruututekstien määrässä ja repliikkijaossa. Lisäksi oletettiin, että tietyn käännösstrategian käytön ja merkityksen muutoksien välillä on yhteys, niin että merkityksen muutoksia esiintyy eniten silloin, kun kaikkea sanottua ei voida kääntää. Tutkielman teoriataustassa esitellään aluksi lyhyesti av-kääntämisen muita lajeja, kuten ns. dubbausta eli jälkiäänitystä, selostusta ja voice-overia, jonka jälkeen syvennytään tekstityksen teoriaan, tekstityksen muotoseikkoihin ja konventioihin sekä tekstityksen käännösstrategioihin. Tekstityksen sisältöseikkojen analyysin viitekehyksenä ovat Henrik Gottliebin (1994, 1997) kymmenen käännösstrategiaa: lisäys (engl. expansion), para-fraasi (paraphrase), suora käännös (transfer), imitaatio (imitation), transkriptio (transcription), siirtäminen (dislocation), tiivistäminen (condensation), lyhentäminen (decimation), poisjättäminen (deletion) ja resignaatio (resignation). Tutkielmassa analysoitiin kaikkien tekstitysversioiden muotoseikat. Tekstityksen sisältöseikkojen tutkimuksessa jokainen dialogin lause tai sivulause analysoitiin omana verbaalisena segmenttinään. Yhteensä analysoitiin 1311 verbaalista segmenttiä ja tutkittiin, mitä käännösstrategiaa missäkin tekstitysversiossa oli missäkin osakäännöksessä käytetty, sekä tarkasteltiin, muuttuuko repliikissä merkitys alkutekstiin verrattuna. Strategiat kuvataan ja niiden käyttöä valaistaan esimerkkien avulla. Tulokset ovat hypoteesia tukevia: Tutkielmassa havaittiin, että kaikkien tekstitysversioiden muotoseikat ovat suurimmalta osin konventioiden mukaisia. Eroja oli havaittavissa tavuviivan, pilkun ja kursiivin käytössä. Versiot eroavat myös ruututekstien määrässä: elokuvaversiossa on eniten ruututekstejä (1091), vaikka siinä on vähiten sanoja (3968); DVD-tekstityksessä on 876 ruututekstiä ja 4278 sanaa ja TV-tekstityksessä on 983 ruututekstiä ja 5293 sanaa. Eroavaisuudet selittyvät sillä, että elokuvatekstityksen ruututekstit ovat lyhyempiä ja nopeammin ilmestyviä kuin DVD- tai TV-tekstitysten. Tutkittu DVD-tekstitys on elokuvatekstityksen muokkaus, mistä johtuu sen vähäinen sana- ja ruututekstimäärä. Tutkielmassa havaittiin myös, että kaikissa versioissa yleisimmin käytetty käännösstrategia oli suora käännös, mutta TV-tekstityksessä sitä oli käytetty yli 50 %:ssa kaikista osakäännöksistä ja DVD- ja elokuvaversiossa yli 35 %:ssa, eli TV-tekstityksessä sitä oli käytetty huomattavasti enemmän kuin muissa versioissa. Lyhentämistä ja poisjättämistä oli DVD- ja elokuvatekstityksessä käytetty enemmän kuin TV-tekstityksessä. Nämäkin erot selit-tynevät elokuvatekstityksen pienemmällä tilalla ja tämän tekstityksen muokkaamisesta DVD-tekstitykseksi. Merkityksen muutoksia ja kaventumisia esiintyi eniten strategioiden poisjättäminen ja lyhentäminen yhteydessä, muiden strategioiden yhteydessä merkityksen muutoksia ja kaventumisia esiintyi vain marginaalisesti. Tulokset tukevat hypoteesia siitä, että merkitys muuttuu ja kaventuu eniten silloin, kun kaikkea sanottua ei voida kääntää.