A fully automated Temperature Dependent Hall (TDH) measurement setup has been assembled for the purposes of this study. This TDH setup is capable of measuring samples in the 20 K to 370 K temperature range. Sample sizes of up to 20 mm × 20 mm can be accommodated by the custom designed and manufactured sample holder. Samples with a resistance in the 1Ω to 250 MΩ range can be measured with this setup provided that the mobility of the sample is greater than 1 cm²/Vs. The computer program controlling the automated measurement processwas written in LabView™ version 6.1. Single crystal Zinc Oxide (ZnO) was the material under investigation in this study. Bulk ZnO samples grown by three different methods, namely pressurized melt growth, seeded chemical vapor transport (SCVT) growth and hydrothermal growth, were measured in the 20 K to 370 K range. The effect of annealing in argon atmosphere in the 550 ºC to 930 ºC range was investigated on all three ZnO types. In addition, hydrogen-implanted layers on semi-insulating hydrothermally grown ZnO were studied. These samples were annealed in the 200 ºC to 400 ºC range and Hall measurements in the 20 K to 330 K range were performed. Programs were written to fit, wherever possible, the obtained temperature dependent carrier concentration and mobility profiles to suitable theoretical models. The carrier concentration data was fitted to a multi-donor single acceptor charge balance equation for the purpose of extracting donor concentrations and activation energies. Before fitting, the data was corrected for the Hall scattering factor and, where necessary, for two-layer effects particularly a degenerate surface conduction channel that developed through annealing on the SCVT-grown and hydrothermally grown samples. The acceptor concentrations of the samples were obtained by fitting the mobility data to a model based on D.L. Rode’s method of solving the Boltzmann transport equation. Scattering mechanisms included in the model were piezoelectric and deformation potential acoustic modes, polar optic modes and ionized impurity scattering. It was found that the mobility data did not fit the model very well without assigning questionable values to other parameters, in this case the deformation potential. Plausible values for the acceptor concentration were however obtained. The carrier concentration data fitted the model well, but due to the large number of parameters to be extracted (up to six parameters in the case of three donors) there was often not much certainty in the extracted values This study shows that TDH analysis is a valuable tool to assess the quality of semiconductors. Bulk and degenerate surface (or interfacial) conduction are separated with relative ease, and shallow defect concentrations as well as compensation level concentrations could be extracted. The generally observed uncertainty in values obtained in the multi-parameter regression of carrier concentration data indicates that supplementary techniques such as photoluminescence are needed to support results obtained by the TDH technique. / Dissertation (MSc (Physics))--University of Pretoria, 2007. / Physics / MSc / unrestricted

This project is focused on computer modeling of so-called meta-materials, and on the exploitation of metamaterials in the design of electrically small antennas. For modeling, COMSOL Multiphysics 3.3 was used. Simulations were focused on impedance matching of antennas. Antennas with metamaterials were compared with corresponding conventional antennas without metamaterial layers. The project does not investigate the creation of metamaterials; the project concentrates on their influence on crucial parameters of antennas. Next step this project is focused on optimalization this structure in program Matlab version R2009b. We used optimalization method PSO (swarms of particles) and results are comparing whit results calculating in COMSOL program.

The main goal of my work is the electrically commutated motor with the vector control’s application in the environment of Matlab – Simulink. The theoretical preamble of this document is dedicated to the physical construction of the EC motors. The most common methods are described in the following text – namely it is scalar control, direct torque control and vector control. The conclusion of this work includes the description and analyse of the single parts of a created model of concrete EC motor with the vector control, and simulations results’ evaluation.

We present a HiLo microscope with an electrically tunable lens for high-contrast three-dimensional image acquisition. HiLo microscopy combines widefield and speckled illumination images to create optically sectioned images. Additionally, the depth-of-field is not fixed, but can be adjusted between widefield and confocal-like axial resolution. We incorporate an electrically tunable lens in the HiLo microscope for axial scanning, to obtain three-dimensional data without the need of moving neither the sample nor the objective. The used adaptive lens consists of a transparent polydimethylsiloxane (PDMS) membrane into which an annular piezo bending actuator is embedded. A transparent fluid is filled between the membrane and the glass substrate. When actuated, the piezo generates a pressure in the lens which deflects the membrane and thus changes the refractive power. This technique enables a large tuning range of the refractive power between 1/f = (-24 . . . 25) 1/m. As the NA of the adaptive lens is only about 0.05, a fixed high-NA lens is included in the setup to provide high resolution. In this contribution, the scan properties and capabilities of the tunable lens in the HiLo microscope are analyzed. Eventually, exemplary measurements are presented and discussed.

The objective of this study was to evaluate and gain a better understanding of the short-term impact performance and the long-term durability of electrically conductive adhesives for electronic interconnection applications. Three model conductive adhesives, designated as ECA1, ECA2 and ECA3, supplied by Emerson & Cuming, were investigated, in conjunction with printed circuit board (PCB) substrates with metallizations of Au/Ni/Cu and Cu, manufactured by Triad Circuit Inc. Effects of environmental aging on the durability of conductive adhesives and their joints were evaluated. All the samples for both mechanical tests and thermal tests were aged at 85%, 100%RH for periods of up to 50 days. Studies of bulk conductive adhesives suggested that both plasticization, which is reversible and further crosslinking and thermal degradation, which are irreversible, might have occurred upon exposure of ECAs to the hot/wet environment. The durability of electrically conductive adhesive joints was then investigated utilizing the double cantilever beam (DCB) test. It was observed that the conductive adhesive joint was significantly weakened following hydrothermal aging, and there was a transition from cohesive failure to interfacial failure as aging continued. A comparative study of the durability of different conductive adhesive and substrate metallization combinations suggested that the resistance of the adhesive joints to moisture attack is related to the adhesive properties, as well as the substrate metallizations. It was noted that the gold/adhesive interface had better resistance to moisture attack than the copper/adhesive interface. A reasonable explanation of this phenomenon was given based upon the concept of surface free energy and interfacial free energy. XPS analysis was performed on the fractured surfaces of DCB samples. For adhesive joints with copper metallization, copper oxide was detected on the failed surfaces upon exposure of the conductive adhesive joints following aging. XPS analysis on the fractured surfaces of adhesive joints with Au metallization suggested that diffusion of Cu to the Au surface might have happened on the Au/Ni/Cu plated PCB substrates during aging. The impact performance of conductive adhesives was quantitatively determined using a falling wedge test. This unique impact resistance testing method could serve as a useful tool to screen conductive adhesives at the materials level for bonding purpose. Moreover, this test could also provide some useful information for conductive adhesive development. This study revealed that the viscoelastic energy, which is a result of the internal friction created by chain motions within the adhesive material, played an important role in the impact fracture behavior of the conductive adhesives. This study also demonstrated that the loss factor, evaluated at the impact environment conditions, is a good indicator of a conductive adhesive's ability to withstand impact loading. / Ph. D.

The construction industry is facing a reality where the dependency on fossil fuels needs to cease and be replaced by options that are more climate friendly. One such option is the electrification that has not made a breakthrough in the construction industry yet and therefore needs to be examined. In this thesis an investigation is made by two different systems of wheel loaders and trucks. One system that conducts machines run by electricity and another one where the system is powered by diesel. The investigation is based on goal formulation which serves as the basis for answering these questions. The machines were examined in such as to obtain results that illustrate which system of machines that are profitable with regards to time, energy consumption, carbon dioxide emissions and total costs. This thesis has also as an intent to identify any advantages and disadvantages of each transport method. This is done in order to lend structure to any further research conducted in the future. To be able to compare and examine the properties of the machines, these machines were applied to a tunneling project. The project that was received was the metro station Hagalunds industriområde. The planned expansion of the subway will lead to a new metro line between Arenastaden and Odenplan, where Hagalunds industriområde will become an intermediate station. In order to truly optimize our efforts and carry out the calculations, the focus was placed on a partial stretch of 1 000 meters with respect to the main tunnel and working tunnel. The result obtained shows that the electric wheel loader leads to less time, carbon dioxide emissions and better energy efficiency than the diesel-powered wheel loader. On the other hand, the disadvantage is that the purchase cost of the electric wheel loader leads to greater total costs. These investments may be necessary to break the dependence on fossil fuels. When comparing the trucks, the result showed that the electric truck is a better alternative from an environmental perspective and total costs. While the diesel-powered truck saves on both time and energy. The reason why the total cost of the diesel-powered truck differs greatly from the electricpowered truck is the rental costs. If the diesel-powered truck was instead purchased, the total cost difference could be reduced. / Bygg- och anläggningssektorn står inför en verklighet där beroendet av fossila bränslen behöver brytas och ersättas med miljövänligare alternativ. Ett sådant alternativ är elektrifieringen som inte riktigt har slagit igenom för anläggningssektorn och därför behöver undersökas. I detta examensarbete undersöks två olika system av hjullastare och lastbilar. Ett system där maskinerna drivs med el och ett annat system med maskiner som drivs på diesel. Undersökningen hade målformuleringen som utgångspunkt för att besvara frågeställningarna. Maskinerna granskades för att erhålla ett resultat som visar vilket system av maskiner som är lönsammare att använda med avseende på tidsåtgång, energiförbrukning, koldioxidutsläpp samt totala kostnader. Examensarbetet har även som syfte att redogöra eventuella för-och nackdelar för respektive transportmetod. Detta för att ge ytterligare underlag till vidare forskning. För att kunna jämföra och undersöka maskinernas egenskaper applicerades dessa maskiner på ett tunneldrivningsprojekt. Projektet som erhölls var tunnelbanestationen Hagalunds industriområde. Den planerade utbyggnaden av tunnelbanan kommer att leda till en ny tunnelbanelinje mellan Arenastaden och Odenplan, där Hagalunds industriområde kommer bli en mellanliggande station. För att avgränsa arbetet och genomföra beräkningarna lades fokus på en delsträcka om 1 000 meter med avseende på huvudtunnel och arbetstunnel. Resultatet som erhölls visar att den eldrivna hjullastaren leder till mindre tidsåtgång, koldioxidutsläpp och bättre energieffektivitet än den dieseldrivna hjullastaren. Däremot är nackdelen att inköpskostnaden för den eldrivna hjullastaren leder till större totala kostnader. Dessa investeringar kan vara nödvändiga att vidta för att beroendet av fossila bränslen ska brytas. Vid jämförelse av lastbilarna visade resultatet att den eldrivna lastbilen är ett bättre alternativ ur miljöperspektiv och totala kostnader. Medan den dieseldrivna lastbilen sparar på både tid och energi. Anledningen till att totala kostnaden för dieseldrivna lastbilen skiljer sig mycket från den eldrivna lastbilen är hyreskostnaderna. Om den dieseldrivna lastbilen istället köptes in, kunde den totala kostnadsskillnaden reduceras.

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No / A miniaturized conical helix antenna is presented, which displays vertical polarization with electrically small dimensions of 10mm×10mm×45mm. The resonance of the antenna is made tunable by adding a variable digital MEMS capacitor load at the bottom of the helix, giving a tuning range of 316 MHz to 400 MHz. The antenna demonstrates considerable impedance matching bandwidth and gain over the entire tuning frequency band. Most importantly, the antenna is capable of compact, flexible and easy integration into a wireless device package or for platform installation. / Datong of Seven Technology Group, for their support under the KTP project grant No. 008734.

Electrically detected magnetic resonance (EDMR) is a sensitive spectroscopic technique, which can be used to readout few to single electron spins in semiconductor and carbon nanodevices for applications in solid state quantum information processing (QIP). Since only electrically active defects contribute to the EDMR signal, this technique can be used further to investigate defects and impurities in photovoltaic devices, in which they limit the sunlight-to-energy conversion efficiency significantly. Here, I employ X-band EDMR for semiconductor defect analysis and identify the most important recombination centres in Czochralski silicon with oxide precipitates, which can be intentionally grown to confine detrimental metallic impurities to inactive regions of the wafer in order to serve as a defect-free substrate for modern silicon photovoltaic devices. Those experiments show that oxide precipitation is accompanied by the formation of silicon dangling bonds. Furthermore, I describe a very promising route towards the fabrication and readout of few to single electron spins in carbon nanotube devices, which can be characterised structurally via transmission electron microscopy in order to relate their electrical and spin properties with their structure. Finally, I employ EDMR to read out electron spin states in donor-doped silicon field-effect transistors as a prerequisite for their application in QIP. I report on a novel cryogenic probe head for EDMR experiments in resonant microwave cavities operating at 0.35 T (9.7 GHz, X-band) and 3.34 T (94 GHz, W-band). This approach overcomes the inherent limitations of conventional X-band EDMR and permits the investigation of paramagnetic states with a higher spectroscopic resolution and signal intensity. Both advantages are demonstrated and discussed. I further report on a novel mechanism giving rise to the EDMR effect in donor-doped silicon field-effect transistors, which is capable of explaining why the EDMR signal intensities of the conduction electrons are enhanced by a factor of ∼100, while the donor resonance signals increase by a factor of ∼20 from X- to W-band only. The spin-relaxation and dephasing times are extracted from a series of pulsed-EDMR measurements and confirm this model. The author gratefully acknowledges funding from Trinity College Oxford, Department of Materials, EPSRC DTA, and Konrad-Adenauer-Stiftung e.V. (Begabtenförderung).