A test scheme to test micro-beams from diatom frustule has been developed. The method is capable of testing both complete beams and beams made from the individual layers of the frustule. The biosilica is shown to be a very brittle material with an average fracture stress of 336 +- 73 MPa and a flexural modulus of 5.72 +- 2.9 GPa. A comparison of the mechanical properties of the different layers has been performed and shows that the different structural parts greatly influence the overall mechanical properties. Additionally the mechanical properties of frustules that have undergone different chemical treatments have been investigated. The initial results indicate that the softer chemical treatment yields a stiffer biosilica. The challenges of computational modeling of biosilica has been discussed and initial FEM-modeling shows that the porous structure reduces the stiffness of the overall structure. Further development of a combined experimental and computational test scheme is suggested. In addition an AFM-study and nanoindentation tests were performed on the frustules.

Control of growth and surface morphology of perovskite oxide thin films is essential for future electronic devices based on such materials. Uncommon crystallographic orientations, like (111), are particularly interesting in order to control domain formations, but have been shown to grow in a rough manner, because of their polar surfaces. This work aims to elucidate the growth mode of (111) oriented systems, to enable smooth surface structured films. We have investigated the growth of La_{0.7}Sr_{0.3}MnO_3 (LSMO) thin films by pulsed laser deposition (PLD) on (111)oriented SrTiO_3 (STO), characterized by AFM and x-ray diffraction. Substrate surface preparation has been optimized to yield uniform straight step-and-terrace surface structures, as well as the ability to tune the surface structure by different surface preparations. The film surface structure is observed to duplicate the substrate surface; hence, control of the film surface structure is obtained. A detailed description of the growth mode, from thin films of only a few mono layers to thick films of 70nm is presented. The growth mode is complex showing in principle an unstable growth. For the first 20 mono layers (2nm) a roughening transition from step-flow to layer-by-layer is observed. At higher thicknesses a second transition is seen, where the surface breaks up to a 3D surface structure. The critical thickness of the second transition is delayed by reducing the deposition temperature, as expected for strained surfaces, resulting in epitaxial thin films of step-and-terraces structure at least 70nm thick. The crystallinity of the films has been confirmed by XRD measurements. The transition to 3D growth is shown to initiate at the step-edges, and stabilizes with step-bunched steps. A speculative discussion of step-induced strain, and consequently the surface breakup is presented. Furthermore magnetic measurements by VSM in room temperature are presented. The saturation magnetic moment is measured to be $330 emu/cm^3$ at room temperature, which is 100 emu/cm3 larger than other reported values for LSMO/STO(111). The improved understanding of substrate preparation and growth mode in LSMO/STO(111) is important for further work on oxide interfaces, as we believe these results can be expanded to other (111) systems. The magnetic measurements give a preliminary indication that high quality films are necessary to exploit the full potential of these materials.

Atmospheric icing from supercooled droplets in the atmosphere can have catastrophic consequences for a number of man-made structures in regions with cold climate and at high altitude, resulting in accidents with both socioeconomic losses and loss of human lives. To mitigate the icing problem, active de-icing involving chemical, thermal and mechanical techniques have been developed to remove ice that has already accumulated. These techniques are sub-optimal, however, as they are plagued with problems such as high energy consumption, hazard to the environment, high economic costs, and need for frequent reapplication. This thesis takes a look at an entirely different approach, namely utilizing superhydrophobic surfaces to reduce or eliminate the accumulation and adhesion of ice from the outset. Much of the research in the field of superhydrophobicity has involved surfaces with open-cell structures, e.g. pillar-like surfaces and surfaces with bumps and valleys. It has been reported that surfaces with closed cells have a comparative advantage in that they are better at retaining their hydrophobic properties under pressure. This thesis investigates the wetting properties (which are often closely tied to icephobic properties) of closed-cell structures further, using LAMMPS simulations. The simulations show that wetting on these surfaces satisfies the well-known theories of Wenzel and Cassie-Baxter. However, on the small scale on which the simulations were carried out, the effect of tuning the roughness scale is not as predicted by theory. Furthermore, no comparative advantage against open-cell structures could be demonstrated for the closed-cell surfaces. A physical experiment was also carried out, in which the influence of water condensation on the dynamic behavior of water droplets on a nearly-superhydrophobic black silicon surface was tested. The results confirm a well-known problem: Condensation severely deteriorates the water repellency of hydrophobic surfaces. The literature review and experiments in this thesis shows that superhydrophobic surfaces have a great potential for use in anti-icing applications, demonstrating delayed freezing, reduced ice accumulation, and reduced ice adhesion. Nevertheless, major problems are yet to be solved, including deterioration of icephobicity due to mechanical damage, and reduced icephobicity in humid conditions.

AlGaAs nanowires (NWs) with axial GaAs inserts, grown with molecular beam epitaxy will be investigated with micro-photoluminescence spectroscopy, including CW and pulsed excitation at cryogenic and ambient temperatures.

The metabolic insertion of titanium into the biosilica frustules of the pennate diatom Pinnularia sp. and the centric diatom Coscinodiscus wailesii was explored in the present study. A total of five titanium incorporation experiments were conducted on Pinnularia, in addition to five control experiments. Titanium dissolved in HCl was co-delivered with silicate dissolved in NaOH to silicate replete and silicate deplete Pinnularia cultures over a 10 hour delivery period. Cell number, silicate and titanium concentration, Quantum Yield, Instantaneous Chlorophyll Fluorescence and pH was measured regularly throughout the experiments. The diatoms were left to consume the delivered silicate/titanium for 62 hours after delivery was completed before they were harvested and rinsed to remove the organic material. The resulting biosilica frustules were analyzed with (Scanning) Transmission Electron Microscopy to investigate the frustule structure, Inductively Coupled Plasma Mass Spectrometry to measure the elemental composition of the frustules and Energy Dispersive Spectroscopy to determine the location of the elements in the frustules. Quantum Yield measurements were conducted to obtain information about the Pinnularia photo system condition, and high Quantum Yield values were interpreted as an indication of a good overall physiological state of the cell. It was found that a combination of high Quantum Yield values and silicate depleted cultures produced the highest titanium content in the Pinnularia frustules (1.3 wt% relative to silicon). Furthermore, EDS analysis revealed that titanium was not evenly distributed throughout the biosilica frustule. The relative titanium content in the Pinnularia frustules was higher in the biosilica at the base of the large pores covering the frustule surface than in the biosilica between the pores. This was in accordance with findings reported in literature. The observed inhomogeneous distribution trend was found to apply also to phosphorous and iron present in the titanium-doped frustules. This observation has not been previously reported.Cell aggregation of the Pinnularia cultures was observed upon silicate/titanium addition. Based on results from control experiments there was reason to believe that the aggregation was triggered by titanium, but the explanation for this cellular response as well as its effect on titanium uptake and incorporation was not determined. Three titanium incorporation experiments were conducted in the proof on concept study on Coscinodiscus . Titanium dissolved in HCl and silicate dissolved in NaOH was co-delivered with a pipette once a day for three, five and seven days. On the day following the final addition, the diatoms were harvested and rinsed before they were analyzed in the same manner as Pinnularia. The experiments on Coscinodiscus revealed that metabolic insertion of titanium into the frustule biosilica was possible, but due to the small maximal titanium content achieved (0.03 wt% relative to silicon) and the slow growth rate, Coscinodiscus was not considered an optimal choice of diatom species for titanium incorporation purposes.It was not possible to rule out whether the frustule structure in any of the two species had been altered or impaired as a consequence of titanium exposure. Structural flaws were observed in frustules with and without titanium incorporated. A faint irregular pattern on the nanoscale was observed in Pinnularia frustules containing titanium. No such pattern was observed in titanium free frustules.The amount of boron measured in the frustule biosilica was higher than the regular dopant concentration in boron-doped silicon. The boron content in Pinnularia was found to be on average 0.1 wt% or 0.28 atomic % relative to Si, while the average in Coscinodiscus was nearly twice as high. Without further manipulation, this high boron natural boron concentration makes diatom frustules unusable for doped semiconductor purposes.Future work should involve reproduction of the obtained results with more replicates, as well as larger culture volumes and, in the case of Coscinodiscus in particular, longer time scale. Titanium uptake and incorporation studies should if possible be performed on single Coscinodiscus cells. Multiple continuous silicate starvation and titanium/silicate delivery cycles should be tested to determine if it is possible to incorporate titanium into a larger fraction of the culture population, as well as to increase the maximum amount of titanium incorporated into one frustule.Aggregation of Pinnularia diatoms should be further investigated to determine reason for the observed reaction, the effects on titanium uptake/incorporation and possible strategies to prevent it from occurring. Pinnularia frustules unexposed to titanium should be inspected in order to determine if the iron and phosphorous distribution pattern observed in the titanium-doped frustules is present in titanium-free frustules as well.A completely artificial culture medium and plastic cultivation containers should be applied to explore how the boron content of diatom frustules can be tailored by controlled delivery of boron to the culture medium.

Monolayer colloidal crystals are formed using silica- and polystyrene beads and used as templates in nanosphere lithography for creating various hexagonal periodic structures intended for light harvesting in crystalline silicon solar cells. Specifically, arrays of silver islands for plasmonic scattering, dimples for use as seeds in electrochemical etching, and silicon cylinders diffraction gratings are fabricated and investigated. Where suitable, optical measurements are done to complement the structural characterisation.

This thesis is a feasibility study of the possible application of magnesium alloys forfuture magnesium-ion batteries. It investigates dierent alloys and characterizesthem with respect to internal resistance, overpotentials and the reversibility of theelectrochemical reaction. SEM and EDS studies of used electrodes have also beencarried out. It has been showed that alloys, easier to handle and at a fraction of thecost, can be used with equal or better performance than pure Mg. The seeminglysuperior alloy, AZ61 exhibits a coloumbic eciency close to 100%, at higher chargerates than pure Mg.

K0:485Na0:485Li0:03Nb0:8Ta0:2O3 powder has been prepared by spray pyrolysis ofaqueous solutions of K/Na/Li nitrates mixed with water soluble Nb and Ta precursors.The as-prepared ceramic powder was calcined at 600 °C to remove any organic residuesafter the spray pyrolysis process. Different milling methods for the calcined powderswere attempted, revealing dry planetary milling to be the most suitable milling method.The powders were characterised using scanning electron microscopy. A complete millingprocess was developed based on sufficient destruction of the egg-shell like agglomerates from the spray pyrolysis process, avoidance of flake formation and reproducibility.Sintering was attempted using three different sintering methods, all using the reverse crucible method to limit the amount of alkali evaporation. An optimal temperature range was found for each of the three, achieving densities in the range of 94-97%. The microstructure of the different samples was explored by polishing the samples and investigating the surfaces by scanning electron microscopy. It was found that the average grain sizes were in the range of a few microns, with large variations in the broadness of the grain size distribution when comparing different sintering methods. For two of the three sintering methods a standard deviation of less than 0.3 micron is reported. An EDS analysis was performed, and it was found that all the samples demonstratecompositional homogenity.Dielectric testing was performed on the samples sintered using the three differentsintering methods. Polishing of the sample surfaces and storage in dessicators had tobe performed in order to avoid moisture influence and achieve reproducibility. Thepiezo- and ferroelectric effect was observed for all the different sintering methods, along with coercive fields in the range of 669 - 889 Vmm and remnant polarizations in the range of 16 - 29 C/cm2 , depending on the sintering method used. A strictly monotonic relationship between average grain size and the coercive field was identified. The normalized strain d*33 was found to be in the range of 230 - 330 pm/V , after poling using an electric field of 4 kVmm at 100 °C. It is argued that on the basis of the present results,K0:485Na0:485Li0:03Nb0:8Ta0:2O3 has potential as a leading candidate for environmentally friendly ferroelectric materials, and spray pyrolysis seems an excellent choice of synthesis method.

High quality surface passivation is important for the reduction of recombination losses in solar cells. In this work, the passivation properties of amorphous hydrogenated silicon nitride for crystalline silicon solar cells were investigated, using electrical characterization, lifetime measurements and spectroscopic ellipsometry. Thin films of varying composition were deposited on p-type monocrystalline silicon wafers by plasma enhanced chemical vapor deposition (PECVD). Highest quality surface passivation was obtained for silicon-rich thin films, where a surface recombination velocity of 30 cm/s was obtained after a heat treatment corresponding to the industrial contact firing process. Electrical characterization of the interface between silicon nitride and silicon was performed by capacitance and conductance measurements. Several challenging aspects related to the interpretation of these measurements were investigated in detail, including charging and discharging, leakage currents, and frequency dependent capacitance.

Multiferroic materials combine two or more ferroic orders such as ferroelectricity, ferromagnetism and ferroelasticity. They have a great interest for the development of the next generations of digital electronic memory devices. Bismuth ferrite has shown to posess both ferroelectric and magnetic order at room temperature, which makes it both scientifically and comercially interesting.The negative impact on the environment by using lead in mass-produced units has made development of lead-free piezoelectric materials for use in sensors, actuators and transducers prioritized and samarium substituted bismuth ferrite has shown to posess a piezoelectric response high enough to be considered for commercial applications. In this project work, 10mol% samarium substituted bismuth ferrite, Bi_{0.9}Sm_{0.1}FeO_{3}, powders have been synthesized using a wet-chemical method and calcined to a range of temperatures to achieve a range of nanocrystalline sizes in the powders. These powders has been investigated using X-ray diffraction (XRD), Rietveld refinement and differential scanning calorimetry (DSC). The powders have also been milled, pressed and sintered to pellets for ferroelectric and piezoelectric testing. The crystal structure was found to belong to the R3c group as for bismuth ferrite, BiFeO_{3}, but the unit cell geometry is changed slightly, and the ferroelectric polarizability is lowered in the case of samarium substitution. This fact is interesting regarding piezoelectricity by thereby increasing the ability to achieve a higher piezoelectric response. No results were achieved from ferroelectric and piezoelectric measurement due to the conductivity found in the sintered pellets were too high, probably due to secondary sillenite phases found in the material. There has been found a finite size effect of a decrease in unit cell volume and tetragonality, of which the decrease in volume is contradictory to the expectations. There is also clear finite size effects on the decrease of cooperative displacement of cations, a measure for the polarization, and for the lowering of the ferroelectric phase transition temperature. The finite size effect for the ferroelectric phase transition has not been reported before. The magnetic phase transition temperature also show a decrease as a clear finite size effect. A linear relationship between electric polarization and magnetic ordering has also been observed in this project. The results from this project contributes to the understanding of material properties of BiFeO_{3} and derived compositions by an investigation of substitution effects and finite size effects. The results presented here motivates further research on these materials.