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Multispectral capabilities of nanowires (NWs) were explored for InAs and InAsSb NWs on Si(111) substrates. NWs were grown with the vapour-solid (VS) growth mode in a molecular beam epitaxy (MBE) system using an oxide template to control positions and diameters. Early attempts to integrate InSb NWs and silicon substrates proved unsuccessful. Instead studies of InAs NWs on silicon, and eventually InAsSb/InAs NWs on silicon were completed to achieve large-diameter, infrared (IR) sensitive photodetectors. InAs NWs were grown on silicon substrates to study their morphology characteristics and vertical NW yield. The five different growth modes explored were (1) Au-assisted vapour-liquid-solid (VLS), (2) positioned Au-assisted, (3) vapour solid, (4) positioned Au-assisted VLS using a patterned oxide mask (VLS-SAE), and (5) selective area epitaxy (SAE) using a patterned oxide mask. Optimal temperature and V/III flux ratios for achieving a high vertical yield were found for the SAE growth mode. Further understanding of the InAs SAE growth mode was gained through modeling of various oxide hole filling scenarios. Each scenario was defined by the arrival rates of the group III and group V materials to the holes. A parameter space is discussed for the growth of high yield InAs NWs, dependent on the V/III flux ratio and temperature of growth. Large diameter InAsSb NWs for IR absorptance were grown on silicon using a high yield InAs stem. Several NW array diameters were grown simultaneously on the same substrate to measure multispectral photodetection. Diameters were controlled by NW spacing. Fourier transform IR (FTIR) spectroscopy was used to measure absorptance in the NWs. NW diameters spanned 440 – 520 nm which resulted in enhanced absorptance in the short-wave IR region. Simulations of the HE11 resonances of the NW arrays were performed and compared with the FTIR measurements. Initial electrical measurements demonstrated a diameter-dependent photocurrent. / Thesis / Doctor of Philosophy (PhD)

As the UN summit in September 2015 addressed with the Sustainable Development Goals (SDG), our planet faces great challenges.[1] Not only since then has the role of synthetic materials chemistry been discussed in this context.[2–16] This not only concerns the development of new materials with outstanding properties such as catalysts, materials for energy conversion, and cost-efficient energy converting and storage materials, but also a reduction of the energy consumption of established functional material syntheses. Therefore, new approaches addressing the three main categories to promote the potential for energy and resource efficiency have been proposed: lowering the temperature of the synthetic processes, improving the yield and purity of the materials, and reducing the amount of waste materials. In this context a number of low-temperature processes have been established, in which mainly solvents, i.e. amines and alcohols, are used in combination with previously synthesised precursors as the solubility of the starting materials limits their usability and most elements are not soluble in these solvents. Novel solvents like ionic liquids (ILs) showcase growing interest as they are considered particularly resource-efficient.[17,18] ILs are defined as liquids that are comprised entirely of ions, with melting points below 100 °C. Continuing on from the reported work in this field, this thesis focuses on investigating the ability of ILs in the syntheses for known chalcogenides at lower temperatures and the synthesis of new materials. The main focus lies on conversions with high atom economy, especially by starting from the elements and completely recycling the IL afterwards, and mechanistic studies elucidating the intermediate dissolved species. Furthermore, as imidazolium based ILs, and their derived LEWIS-acidic ILs [BMIm]Cl/nAlCl3 mixtures, have proven to be good crystallisation media in inorganic syntheses, and the class of mostly room-temperature liquid ILs (RTILs) based on phosphonium cations [P66614]Cl showcased the ability to dissolve red phosphorous, Pred, and the heavier chalcogens S, Se, and Te, this work mainly focuses on these two IL systems. This was also chosen as an in-depth understanding of the activation and resource-efficient synthesis of these chalcogenides has still not been established. As they are RTILs, they also made the characterisation of the reactive and dissolved species by liquid state NMR, Raman, UV/Vis spectroscopy and electrochemical characterisation possible. This expands the knowledge of which main group elements and ore-like starting materials can be used in ionothermal synthesis. As a starting point the thermoelectrically interesting materials class of tellurides is addressed. The under normal conditions hard to dissolve element tellurium readily dissolves in phosphonium ILs with the cations [P66614]+ and [P4444]+. In ILs with carboxylate anions a deep purple hue of the IL already occurred by dissolving tellurium at temperatures of 60 °C. Investigations on the solutions in the acetate ILs revealed the formation of tellurium anions (Ten)2– with chain lengths up to at least n = 5, which are in a dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an IL reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. However, the spectroscopic detection of tellurium cations in these solutions is difficult, but the coexistence of tellurium cations, such as (Te4)2+ and (Te6)4+, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient in stabilizing both types of tellurium ions in solution.[19] In contrast, the acetate ILs show insufficient conversion in reactions of coin metals (Cu, Ag, Au) with tellurium to the corresponding tellurides, especially at low temperatures, however the chloride ILs successfully synthesise Cu2–xTe, CuTe, AuTe2 and Ag2Te. As the synthesis of the tellurides in neat ILs at temperatures down to 60 °C was only sufficient for the system Ag-Te, with a full conversion of the elements to Ag2Te, this was chosen as a model system for further investigations. Even at room temperature, a quantitative yield was achieved by using either 2 mol% of [P66614]Cl in dichloromethane or a planetary ball mill. The unexpected finding that phosphane-free [P66614]Cl also allows the quantitative synthesis of Ag2Te at 60°C implies an additional activation mechanism independent from the phosphane, which is yet unknown.[20] Subsequently, the manifoldly-used lighter chalcogen sulphur is tested for the synthesis of sulphides. Direct synthesis of binary sulphides of B, Bi, Ge, Mo, Cu, Au, Sn, In, Ti, V, Fe, Co, Ga, Ni, Al, Zn, and Sb in [P66614]Cl was tested at 100 °C, i.e. below the melting point of sulphur. Under these conditions, substantial sulphide formation occurred only for nickel (Ni3S4, Ni3S2, NiS) and copper (Cu2S, CuS). Sb showed no formation of crystalline sulphide, but after addition of EtOH, an orange material precipitated which was identified as amorphous metastibnite.[21] As generating these elements from their ores is highly energy consuming, direct dissolution experiments of the crystalline stibnite in [P66614][OAc] and Cl– were investigated and resulted in yellow solutions, from which the amorphous form can be precipitated upon exposure to EtOH air without any sign of decomposition of the IL. In particular, follow-up investigations were conducted on the solubility of Sb2S3 for follow-up chemistry in the LEWIS-acidic IL [BMIm]Cl · 4.7 AlCl3 at 160 °C which resulted in the formation of the novel chloride-terminated [Sb13S16Cl2]5+ quadruple-heterocubane cation-containing compound [Sb13S16Cl2][AlCl4]5.[21] Addition of CuCl in a slightly modified reaction resulted in the formation of the layered semiconductor Cu(Sb2S3)[AlCl4]. From this the AlCl3 can be leached by treatment with 0.1 molar hydrochloric acid, yielding a compound with the presumed composition Cu(Sb2S3)Cl.[22] As ILs showed to be able to activate elements that are insoluble in common solvents, and the formation of Sb2S3 from reactions mixtures of the elements raised the question of whether only the sulphur forms a mobile species or if antimony could additionally activated, the synthesis of binary antimony compounds directly from elements was explored as they are highly discussed as replacements for silicon-based semiconductors. Therefore the 12 elements Ti–Cu, Al, Ga, In, and Te, which are known to form binary compounds with Sb, were reacted with Sb in [P66614]Cl under inert conditions in a simple closed glass flask with vigorous stirring for 16 h at 200 °C. This resulted in the formation of NiSb, InSb, Cu2Sb and Sb2Te3. The applied reaction temperature is several hundred degrees below the temperatures required for solvent-free conversions. Compared to reactions based on diffusions in the solid state, reaction times are much shorter. The IL is not consumed and can be recycled. Since the reaction with Cu showed almost complete conversion, the influences of reaction time, temperature and medium were further investigated. In a diffusion experiment, Cu2Sb formed on the copper, which indicates that antimony forms mobile species in these ILs. These systematic studies hence deliver a contribution to how ILs can help in the synthesis of new materials and how they can make a difference in the synthesis of inorganic materials as well in the context of “GREEN CHEMISTRY”. This can help in developing a more educated choice/toolbox of IL systems for reducing energy costs by reducing the temperature from high temperature inorganic syntheses to syntheses near room-temperature by using the elements as starting materials, with a high atom economy for the synthesis of known and new materials.

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. For instance, in the case of memory devices based on capacitive components, such as static and dynamic random access memories, the dielectric constant will ultimately decide the level of miniaturization. In this context, the observation of anomalously high dielectric constant (>10) in the double perovskite Sr2SbMnO6 (SSM) over wide frequency (100 Hz1 MHz) and (190373 K) temperature range has attracted a great deal of attention. However, unfortunately their dielectric losses were also high which limit their use for possible capacitor and related applications. The dielectric loss however was known to decrease with decreasing crystallite size in electroceramics. Therefore, the present work has been focused on the synthesis of nanocrystalline SSM powders by moltensalt route. The characterization of the ceramics fabricated from these powders for their microstructural and dielectric properties. A cubic phase of SSM powder was obtained by calcining the as synthesized powders at 900°C/10h by using sulphate flux. The crystallite size was ~ 60 nm. The activation energy associated with the particle growth was found to be 95 ± 5 kJmol-1 . The ceramic sintered at 1075°C/16h exhibited high dielectric constant (>10at 1 kHz) with low loss (0.72 at 1 kHz) at room temperature. The results are interpreted in terms of a twolayer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance and modulus formalisms to the grain and grain boundary effects, respectively, while the detected Debyelike relaxation and large dielectric constant were explained in terms of MaxwellWagner relaxation.

In recent years, environmental authorities in Sweden are reporting about high content of antimony in waste water that is discharging from polyester textile dyeing industries. It is known from available scientific publications that, antimony and its compound is harmful for both human and environment. While dyeing of polyester textiles have a commercial importance and in regards to the environmental issues, the industries are looking for the factors those results in high concentrations of antimony in their dyeing waste water. Dyeing of polyester textile requires high-temperature application in association with dyes and process aid chemicals. The waste water that is being produced after dyeing contains a complex mixture of chemicals, where antimony is one of that mixture. To comply with the industries interest, this master thesis work involved the exhaust dyeing of polyester fabrics/yarns and analyzing the dyeing waste water, to determine the amount of antimony diffusion. According to literature studies, the antimony compounds are widely used as catalyst for polyethylene terepthalate (PET) polymerization and hence antimony is present in polyester textiles. The entire experimental work intended to understand the variation of antimony concentration and the factors that are causing high antimony diffusion from polyester textiles during dyeing. The materials which are polyester yarn and fabrics were collected from 3 different dyeing industries of Sweden and the materials were in 9 different types. From material analysis (before dyeing) it has been found there were variations in antimony concentration among the materials. The process parameters that have varied during exhaust dyeing were dyeing temperature, cycle time and process aid chemical (leveling agent) adding options. With the variation in process parameters, the dyeing has performed and the dyeing waste waters have analyzed through inductively coupled plasma sector field mass spectroscopy (ICP-SFMS). The expectations from the experiments were, under specific dyeing process and with same antimony concentration, the materials varying in filament/fiber diameter; big diameter filament/fiber will diffuse less antimony compared to the small diameter filaments. Also, process-wise the antimony diffusion ratio among the materials will accordingly follow the Fick’s diffusion model. To face the environmental issues with sustainability, entire thesis work could provide concentrated knowledge’s with literature evidence for the dyeing industries. As literature study indicates, the dyeing temperature, temperature ramp set and cycle time play major factor while comparing for the expected diffusion ratio. As a gentle process parameter, comparatively lower temperature and cycle time results lower antimony diffusion. The use of levelling agent could be reduced to a level with the appropriateness while added for dyeing. Also, a strong follow-up is needed in the supply chain, for lowering the initial antimony content in the materials. Overall, the findings of this thesis work also keep an importance to do further research on the polyester textile, as during the experiments most of the materials haven’t reacted accordingly as they were expected to react with the Fick’s diffusion model.

Understanding the effects of the process parameters on the distribution behaviour of antimony between metal and slag in the iron blast furnace is critical to develop a universal method of controlling temper embrittlement in commercially pure low alloy steels.

It is important to optimize glass compositions for their specific purpose but also for the efficiency of the production process, the manufacturing of glass. This will be beneficial economically and environmentally. Today many processes and glass compositions are already optimized, but due to more strict legislation on toxic elements and substances there must be changes in many glass compositions. One of these elements is antimony; the oxide is used as fining agent to obtain a bubble free glass within a reasonable process time. One aim with this thesis is to obtain a deeper understanding of the fining mechanism in 20R2O-10MO-70SiO2 (R=Na and/or K, M = Ca and/or Ba, Mg, Sr) glasses in order to minimise the amount of Sb2O3. Another intention is to study the structure of 20R2O-10CaO-70SiO2 (R = Na, K) with Cu2+ as probe ion and thus get a deeper knowledge of the surrounding glass matrix.  The optical basicity scale is used to determine the acid/base character of the different glass compositions.   Fining efficiency results showed a remarkable increase of the number of remaining bubbles when the glass contains either approximately equal amounts of Na and K or Ca and Ba, Mg or Sr. The much higher number of bubbles in the potassium containing glasses compared to the sodium containing is explained by the increase in viscosity, the increase in optical basicity and thus lower oxygen activity. The differences in the fining efficiency when altering alkaline earth ions cannot be explained by the optical basicity values, it seems to be a more complicated situation.   This thesis also reports maximum in Vickers hardness and packing density as well as minimum in glass transition temperature for the mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear nonlinear behaviour. Raman spectroscopy measurements showed a variation in the network connectivity which has a clear relation to the optical basicity of the different glass compositions. The combination of UV-Vis-NIR and X-ray absorption spectroscopy measurements showed that the coordination sphere for Cu(II) is a tetragonal distorted octahedron with two elongated Cu-O bonds along the z axis. There were no trends in the degree of tetragonal distortion, thus it was about the same for all the investigated glass compositions. Cu(I) is found to be coordinated by two oxygen ligands in mainly linear coordination sphere, evidenced from X-ray absorption spectroscopy.

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