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Czochralski (Cz) silicon wafers are used almost exclusively for the fabrication of VLSI devices. Such silicon contains excess oxygen which precipitates as oxide particles either when the initial ingot is grown or subsequently during the wafer device fabrication. Such oxide particles can produce reduced device performance or failure if they occur within the active device regions. However, they can be used to improve the device performance by a process known as internal oxide gettering. The wafers are given a series of preanneal treatments to produce controlled precipitation in which a surface zone of the wafer to a depth of typically in the range of 10 to 50 μm is denuded of oxide particles, while the remainder of the wafer contains large numbers of well formed particles. The devices are fabricated in the surface denuded zone and harmful contaminating metal impurities are attracted during the heat treatment stages away from the device regions to precipitate at the underlying oxide particles or their associated dislocations. In this way device yields can be significantly increased. Because of the importance of these oxide particles and the oxygen precipitation process for VLSI fabrication, considerable efforts have been made to develop methods to assess the numbers and distributions of such particles within the wafers. The number density range of most interest is 10⁷ to 10¹⁰ cm^-3, and the particle size range is typically 30 to 300 nm. The method that has mostly been used is surface etching followed by optical microscopy to obtain etch pit densities. Transmission electron microscopy is a research method used for obtaining detailed information concerning a small number of individual particles. However, because these methods are destructive, much attention has been given during the last few years to the development of infra-red microscopy methods to directly image the particles within the silicon wafers. Although the particles are smaller than the resolution of these methods, individual particles can nevertheless be imaged. This is because the particles are mostly further apart than the resolution limit, and the sensitivity can be sufficient high that adequate contrast occurs. The contrast arises from scattering or absorption of the light by the particle. Infra-red imaging methods developed include infra-red microscopy (IRM), laser scattering tomography (LST), optical precipitate profiler (OPP) and scanning infra-red microscopy (SIRM), all described more fully in Chapter 2. The SIRM has been developed and used to investigate a variety of semiconductor specimens in the Materials Department, Oxford University, during the last ten years. The SIRM has a good performance and flexibility making it especially suitable as a research instrument. Although all of these infra-red imaging methods have been successful to different degrees in assessing oxide particles in Cz silicon wafers, their performance has at least initially been assessed by comparing the number densities and distributions thus obtained with the corresponding results produced by etch pit studies. Furthermore, no serious attempt has yet been made to develop a rigorous theory of the imaging process and to compare the predictions with the experimental images. One of the main objectives of the present work is to do this or at least to make a significant start to such a project based on the SIRM. The outline of an ideal project which aims at a full understanding of the imaging process and the contrast mechanisms is as follows. The performance of the present Oxford SIRM should be improved and the number of imaging modes increased. The improved performance, i.e. better lateral and depth resolutions and higher sensitivity, would enable smaller particles and higher number densities to be imaged, and hence better quantitative data obtained. The larger number of imaging modes would enable the optimum method to be used to image different types of particle. A rigorous theory should be developed that can describe the imaging process and the contrast mechanisms. First, the illumination system should be studied, and in particular the structure of the focussed probe within the specimen and how the structure changes on focussing deeper into the specimen. Second, the interaction of the light with the specimen should be investigated and especially how light is scattered by individual oxide particles in silicon for the case of the particle size being smaller than the light wavelength. Third, the detection system should be considered. For example, for the reflection confocal SIRM, how the light back scattered by the particles is collected by the probe forming lens and imaged at a pin-hole aperture placed in the front of the detector. Well designed experiments are required to determine the imaging properties of the different modes and comparisons should be made between the experimental and theoretical data. The successful conclusion of such a project would enable SIRM images of the particles to be more fully interpreted and hence more detailed information obtained concerning the particles. Furthermore, the images expected from different types of particle could be more closely predicted, e.g. whether they are detectable or not, and hence materials projects could be better planned at the outset. In this thesis we describe the methods that are presently being used to assess oxide particles in bulk silicon (Chapter 2). We review the literature on scanning optical microscopy covering both visible and infra-red light, present some considerations regarding the design of a high performance and versatile SIRM, and describe the various microscope modes that have been or could be used to image particles in semiconductors with infra-red light (Chapter 3). We give a detailed rigorous theoretical analysis of the energy distributions in the probe for the case when the light is focussed by a high numerical aperture lens from air into silicon (Chapters 4, 5). Numerically computed distributions are obtained to illustrate how the probe changes under different conditions, e.g. different focussing depths (Chapter 6). The relationship between the penetration depth of the probe and the spherical aberration coefficient arising from the silicon specimen is determined (Chapter 7). The classical theory of light scattering is applied to individual spherical silicon dioxide particles embedded in silicon. Numerical results are presented and a contrast mechanism is proposed to describe how the scattered intensity depends on particle size (Chapter 8). A formal solution relevant to the reflection confocal SIRM is given to treat the backward propagation of light using a model which takes into account the polarisation state of the incident light, the spherical aberration introduced by the silicon wafer, the polarisation state of the scattered light and the size of the pin-hole (Chapter 9). Experimental results are obtained for most of the imaging modes described in Chapter 3, specimens being selected so that the wide range of the imaging capabilities of the SIRM is shown, and experimental contrast values are compared with theoretical values (Chapter 10). Finally, overall conclusions are drawn and suggestions are made for completing the work started here (Chapter 11).

This thesis covers the development of high-resolution model spectra of simple-stellar-populations (SSP) to be used in the measurement of the ages, metallicities and chemical abundances of unresolved extragalactic globular clusters (GCs). The models are compared to low- and high-resolution spectra of GCs in the Milky Way and M31 galaxies, whose properties are already known, to establish the effectiveness of both the SSP spectral grid and of the direct spectral fitting procedure employed in this work. The model SSP spectra were created using Dotter et al. (2007) isochrones, populated using the flux derived from a grid of stellar spectra, weighted by the Kroupa (2001) mass function. Models with varying mass loss from the red giant branch and varying numbers of He-burning stars were generated. The spectral grid currently covers a parameter range of 2 to 15 Gyrs in age, and -2.5 to 0 dex in [Fe/H] at an [alpha/Fe] of +0.4 dex. Metallicities derived for Milky Way GCs from Lick index comparisons to the model grid are in good agreement with values in the literature. The stellar spectral grid, from which the GC spectra are generated, has been created using ATLAS9 and SYNTHE. The spectra are at a resolution of R = 100,000 and cover a wavelength range from 3000 - 9000 Angstroms. Extensive work was undertaken in creating appropriate lists of atomic and molecular transition oscillator strength (log gf) values for this spectral grid. An automated program was created to alter the strengths of millions of atomic transition lines in the Kurucz atomic line lists to fit a model spectrum of appropriate parameters to that of the red-giant star Arcturus and to the Solar spectrum at shorter wavelengths (3000 - 3727 Angstroms). Comparisons to these observed spectra were made manually for several molecular lines and band-heads, and log gf values changed en-mass for all the lines of a given molecular species. The SSP spectra were compared to low-resolution spectra of Milky Way GCs. Integrated-light spectra of a large number of Galactic GCs were obtained from three sources: the Schiavon et al. (2005) Library of Integrated Spectra of Galactic Globular Clusters, taken using the Ritchey-Chretien spectrograph on the Blanco 4m telescope at Cerro Tololo Inter-American Observatory; spectra obtained through private communication with M. Bessell using the Double Beam Spectrograph on the 2.3m telescope at Siding Springs Observatory; and spectra obtained using the Robert Stobie Spectrograph on the 11m diameter Southern African Large Telescope. With resolutions of 1500 to 2800, abundances of individual elements could not be determined, but overall ages and metallicities were derived. The model spectra were fitted to the observed spectra using a Chi^2 minimisation procedure over large wavelength regions to fully utilise the information available in the spectra. Derived metallicity values were in agreement with literature values. However, age determinations were not consistent with those derived from photometric methods and had large associated uncertainties. The lack of age information in the spectra at such resolutions is a similar result to that found by other studies using the Schiavon data (eg. Mendel et al., 2007; Koleva et al., 2008). The SSP spectral grid was used to determine ages, metallicities and individual elemental abundances of three clusters (GCM06, GC5 and GC10) in the outer halo of M31. High-resolution spectra from Keck-HIRES were obtained through private communication with D. Forbes. Age and metallicity determinations were made simultaneously by fitting un-blended FeI lines and the H-beta and H-gamma lines. Diagnostic analysis (such as that done by Colucci et al., 2009) and simultaneous fitting of the FeI lines alone gave unrealistic age values that tended towards the lower limits (2 Gyrs) of the age grid. The age and metallicities derived in this work for these clusters are consistent with those found by Alves-Brito et al. (2009) using the same data. Abundances of a number of elements were derived from the high-resolution spectra. An overall enhancement of alpha-elements (from measurements of Ca, Si and Ti) was seen in all three clusters ([alpha/Fe] = 0.67 +/- 0.2, 0.63 +/- 0.2 and 0.5 +/- 0.2 dex for clusters GCM06, GC5 and GC10 respectively) which is greater than that found for other M31 GCs (Puzia et al., 2005; Colucci et al., 2009). A depletion in Mg compared to the other alpha-elements is seen, in accordance with patterns seen in both Milky Way and M31 GCs (Gratton et al., 2004; Colucci et al., 2009). All three clusters show varying levels of enhancements and depletion in the other measured elements (C, Sc, V, Cr, Mn, Ni, Ba), none of which follow the trends seen in Milky Way clusters. Comparisons to high-resolution spectra of Milky Way GCs, for which abundance ratios are known from the measurement of individual stars, need to be made to establish the accuracy of this elemental-abundance analysis. Overall, the system presented in this thesis is well designed to be used in the analysis of integrated-light spectra from distant, unresolved GCs. The uncertainties in the derived ages are still larger than desired, but the metallicity determination is very consistent when tested against clusters of known metallicities.

Leaf senescence is the final stage of leaf development, during which the leaf relocates most of itsvaluable nutrients to developing or storing parts of the plant. As this process progresses, leaves losetheir green color and their capacity to perform photosynthesis. Shade and darkness are well-knownas factors inducing leaf senescence and it has been proposed that senescence can be initiated byreductions in photosynthesis, photomorphogenesis and transpiration. However, despite the fact thatthe signaling mechanisms regulating each of these processes have been extensively described,particularly in seedlings, their contribution to the initiation of senescence in mature leaves stillremains unclear. Furthermore, the use of different experimental systems to study shade-inducedleaf senescence has yielded several divergent results, which altogether complicate the overallunderstanding of leaf senescence. To address this, darkened plants and individually darkened leaves, which show different rates of leafsenescence, were studied. Comparing the transcriptome and metabolome of these two darktreatmentsrevealed that they differed distinctly with regard to their metabolic strategies. Wholedarkened plants were severely carbohydrate-starved, accumulated amino acids and slowed downtheir metabolism. In contrast, individually darkened leaves showed continued active metabolismcoupled to senescence-associated degradation and relocation of amino acids. This knowledge was used to set up a new system to study how shade affects leaf senescence in themodel plant Arabidopsis thaliana. Use of this system revealed that different senescence-associatedhallmarks appeared in response to different intensities of shade. Some of these hallmarks werefurther shown to be part of both leaf senescence and photosynthetic acclimation to low light. Finally, using this system on phytochrome mutants revealed that loss of phytochrome A increasedthe loss of chlorophyll under shade, without increasing the expression of senescence-associatedgenes. Together, these findings suggest that shade-induced leaf senescence, which is generally perceived asa single process, is actually an intricate network of different processes that work together tomaintain an optimal distribution of nutrients within the plant.

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Companies constantly strive for the perfect order which enables them to satisfy and retain their customers. This is a difficult process that can be facilitated by using different picking technologies. In this study, a research of the picking technologies Pick-to-Light and Pick-to-Voice have been made to investigate when each technology is suited.In order to collect relevant information and data to be able to answer the question formulation, a qualitative study with interviews have been made. The purpose of this essay was to investigate Pick-to-Light and Pick-to-Voice to see when each technology is best suited and to see what the differences between the technologies are. With our essay we wanted to help manufacturing companies to make the right decisions when implementing a picking technology.The results showed that those picking technologies give companies a higher picking quality and an increased work efficiency since the order picking is faster to perform, and that picking errors are reduced. Through the interviews conducted, the result showed that Pick-to-Light and Pick-to-Voice are best suited at different types of areas. Pick-to-Light is optimal in small areas with high picking frequency while Pick-to-Voice is optimal in large areas with low picking frequency. Companies that are thinking of expanding in the future and use a picking technology on a much larger area, was recommended to implement Pick-to-Voice since this technology is more cost effective. Both of these technologies have multiple positive effects that are similar. Examples on these positive effects are that the operator has an overview of the items to be picked, the technologies are easy to learn and ergonomics are enhanced significantly when all paper handling is eliminated.Obviously, there are also differences between the techniques and also some disadvantages of each technique. The main differences are that the operator with Pick-to-Light can see which articles to be picked with the help of the luminous lights while the operator with Pick-to-Voice is voice guided to the items to be picked. Another major difference is that Pick-to-Voice is a wireless technology unlike Pick-to-Light and the ability to pick multiple orders at the same time is only possible with Pick-to-Voice. When it comes to maintenance costs, Pick-to-Light is more costly, both in time and money, since lights and cable must be replaced periodically. Likewise, an expanding with Pick-to-Light is more comprehensive since more cables and lamps must be purchased and installed. With Pick-to-Voice the only needed adjustment to make is in the system.Depending on the available conditions on the companies, the technologies are best suitable in different ways. Companies can use the technologies to secure the quality of the picking, reducing picking errors, and streamline the picking process. These technologies create the opportunity for companies to achieve the perfect order.

This creative project presents a comprehensive and detailed guide to the building of inexpensive studio lighting equipment. The projects include simple equipment such as backgrounds, snoots and scrims to more specialized equipment like the glassware table and softlight box.Each project includes figures and instructions for building the equipment. At the end of each project are examples of the effects of each piece of equipment in a photographic situation.Also included is a list of photographic data on how each of the photographs was taken.