Dissertations / Theses on the topic 'Ga-Free'

The buffer layer in Cu(In,Ga)Se2 solar cells can improve cell performance. In this work we make CdS buffer layer by chemical bath deposition (CBD) without ammonia. CBD without ammonia were sought out since ammonia is a volatile compound. Different recipes for making CdS were tested; only one of the tested recipes actually produced something that is worth further investigating. This recipe used sodium citrate, an innocuous compound instead of ammonia. The best performance was 0.15 % off from the reference.This is almost as good as the used baseline process. However the worst almost completely killed the solar cells. Cell performance dropped by more than absolute 10 %. This demonstrates that chemical bath deposition can have profound effects on the solar cell performance. When trying to improve the best cells only detrimental effects showed up. This might show that, a part in the recipe used, NaOH has detrimental effects on solar cells. Ammonia free chemical bath deposition is possible, however so far it has not produced as good results as the reference. The difference is however very small, which makes it worth further investigating with moreand better solar cell material.

A deeper understanding of Cu(In,Ga)Se2 (CIGS) solar cells is important for the further improvement of these devices. This thesis is focused on the use of electrical modelling as a tool for pursuing this aim. Finished devices and individual layers are characterized and the acquired data are used as input in the simulations. Band gap gradients are accounted for when modelling the devices. The thesis is divided into two main parts. One part that treats the influence of cadmium free buffer layers, mainly atomic layer deposited (Zn,Mg)O, on devices and another part in which the result of CIGS absorber layer modifications is studied. Recombination analysis indicates that interface recombination is limitting the open circuit voltage (Voc) in cells with ZnO buffer layers. This recombination path becomes less important when magnesium is introduced into the ZnO giving a positive conduction band offset (CBO) towards the CIGS absorber layer. Light induced persistent photoconductivity (PPC) is demonstrated in (Zn,Mg)O thin films. Device modelling shows that the measured PPC, coupled with a high density of acceptors in the buffer-absorber interface region, can explain light induced metastable efficiency improvement in CIGS solar cells with (Zn,Mg)O buffer layers. It is shown that a thin indium rich layer closest to the buffer does not give any significant impact on the performance of devices dominated by recombination in the CIGS layer. In our cells with CdS buffer the diffusion length in the CIGS layer is the main limitting factor. A thinner CIGS layer improves Voc by reducing recombination. However, for thin enough absorber layers Voc deteriorates due to recombination at the back contact. Interface recombination is a problem in thin devices with Zn(O,S) buffer layers. This recombination path is overshadowed in cells of standard thickness by recombination in the CIGS bulk. Thin cells with Zn(O,S) buffer layers have a higher efficiency than CdS cells with the same absorber thickness.

Une augmentation de la température de fonctionnement des matrices de détecteurs infrarouges (IR-FPA) refroidis haute performance conduirait à une réduction de la taille, du poids et de la consommation énergétique de la machine à froid ce qui permettrait d'accéder à de nouvelles applications où les besoins des caméras IR en termes de portabilité, de compacité et d'autonomie énergétique sont essentielles. Actuellement, les technologies de photodétecteurs fonctionnant à haute température (T = 150K), en particulier le détecteur InAsSb, ne couvrent qu'une partie du domaine spectral du moyen infrarouge (MWIR), pour des longueurs d'ondes en deçà de 4,2 μm. Etendre la longueur d'onde de coupure à la totalité du domaine MWIR, jusqu'à 5 μm pour une température de fonctionnement au moins égale à 150K, sans dégradation de performance, présenterait des avantages radiométriques indéniables. En associant les avantages des superréseaux (SR) de matériaux semiconducteurs, en particulier en ce qui concerne la flexibilité en longueur d'onde de coupure de ces nanostructures périodiques, avec ceux des nouvelles architectures de structures à barrière, appelées XBn, la thèse a pour objectif de fabriquer et d'étudier les premiers photodétecteurs 'Ga-free' (sans Gallium) à base de superréseau de type II InAs/InAsSb (T2SL). Le photodétecteur à SR 'Ga-free' sur substrat GaSb est réalisé dans une configuration XBn avec une longueur d'onde de coupure à 5 μm et montre des performances en courant d’obscurité et en rendement quantique à l’état de l’art mondial
An Increase of the operating temperature of the high performance cooled infrared (IR) detector focal plane arrays (FPAs) would induce a reduction in size, weight and power consumption of the cryocooler and allow a new class of applications where the needs in portability, compactness and energy autonomy of the IR cameras are essential. Currently, the photodetector technologies operating at high temperature (T= 150K), in particular the detector based on InAsSb, only cover a part of the midwave infrared (MWIR) domain, below 4.2µm. The extension of the cutoff wavelength to the full MWIR spectrum until 5µm for an operating temperature equal to 150K or higher, with no tradeoffs in performance, would present evident radiometric advantages. Combining the advantages of superlattice (SL) nanostructures in term of tuning of cut-off wavelength and the ones of XBn barrier structure device, the main objective of the thesis is to fabricate and study the first Ga-free InAs/InAsSb type-II superlattice (T2SL) photodetector. The Ga-free T2SL photodetector on GaSb substrate is used in a XBn configuration with a 5 µm cutoff wavelength and showing state of the art performance in terms of dark current and quantum efficiency

CdS is conventionally used as a buffer layer in Cu(In,Ga)Se2, CIGS, solar cells. The aim of this thesis is to substitute CdS with cadmium-free, more transparent and environmentally benign alternative buffer layers and to analyze how the material properties of alternative layers affect the solar cell performance. The alternative buffer layers have been deposited using Atomic Layer Deposition, ALD. A theoretical explanation for the success of CdS is that its conduction band, Ec, forms a small positive offset with that of CIGS. In one of the studies in this thesis the theory is tested experimentally by changing both the Ec position of the CIGS and of Zn(O,S) buffer layers through changing their gallium and sulfur contents respectively. Surprisingly, the top performing solar cells for all gallium contents have Zn(O,S) buffer layers with the same sulfur content and properties in spite of predicted unfavorable Ec offsets. An explanation is proposed based on observed non-homogenous composition in the buffer layer. This thesis also shows that the solar cell performance is strongly related to the resistivity of alternative buffer layers made of (Zn,Mg)O. A tentative explanation is that a high resistivity reduces the influence of shunt paths at the buffer layer/absorber interface. For devices in operation however, it seems beneficial to induce persistent photoconductivity, by light soaking, which can reduce the effective Ec barrier at the interface and thereby improve the fill factor of the solar cells. Zn-Sn-O is introduced as a new buffer layer in this thesis. The initial studies show that solar cells with Zn-Sn-O buffer layers have comparable performance to the CdS reference devices. While an intrinsic ZnO layer is required for a high reproducibility and performance of solar cells with CdS buffer layers it is shown in this thesis that it can be thinned if Zn(O,S) or omitted if (Zn,Mg)O buffer layers are used instead. As a result, a top conversion efficiency of 18.1 % was achieved with an (Zn,Mg)O buffer layer, a record for a cadmium and sulfur free CIGS solar cell.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 717

Ferroelectric (piezoelectric) and ferromagnetic materials have extensively permeated in modern industry. (Na1/2Bi1/2)TiO3-BaTiO3 (NBT-x%BT) single crystals and K1/2Na1/2NbO3 (KNN) textured ceramics are top environment-friendly candidates which have potential to replace the commercial lead zirconate titanate or PZT. High magnetostrictive strain (up to 400 ppm) of Fe-xat.%Ga makes this alloys promising alternatives to existing magnetostrictive materials, which commonly either contain costly rare-earth elements or have undesirable mechanical properties for device applications. These systems have common characteristics: compositional/thermal/ electrical dependent structural heterogeneity and chemical disorder on sub-micron or nano scale, resulting in diverse local structures and different physical properties. In this work, I have investigated domain and local structures of NBT-x%BT crystals, KNN ceramics and Fe-xat.%Ga alloys under various conditions, mainly by scanning probe and electron transmission techniques. In NBT-x%BT single crystals, polarized light, piezo-response force (PFM) and transmission electron (TEM) microscopies were used to study domain structures and oxygen octahedral tiltings. Hierarchical domain structures were found in NBT: a high-temperature tetragonal ferroelastic domain structure is elastically inherited into a lower temperature rhombohedral ferroelectric phase. Nanoscale domain engineering mechanism was found to still work in NBT-x%BT system and a modified phase diagram was proposed based on domain observations. An increased intensity of octahedral in-phase tilted reflections and a decrease in the anti-phase ones was observed, with increasing x as the morphotropic phase boundary (MPB) is approached. It was also found that Mn substituents favor the formation of long range ordered micro-sized ferroelectric domains and octahedral in-phase tilted regions near the MPB. Nano-size heterogeneous regions were observed within submicron domain structure, indicating that the nanoscale polarization dynamics are not confined by domain boundaries, and the high piezoelectricity of NBT-x%BT is due to a polarization dynamics with high sensitivity to electric field and a broadened relaxation time distribution. In KNN textured ceramics, an aging effect was found to exist in the orthorhombic single phase field, not only in the orthorhombic and tetragonal two-phase field as previously reported. No variation of phase structure was revealed between before and after aging states. However, pronounced changes in domain morphology were observed by both PFM and TEM: more uniform and finer domain structures were then found with aging. These changes were even more pronounced after poling the aged state. A large number of sub-micron lamellar domains within micron-domains were observed: suggesting a domain origin for improved piezoelectric properties. In Fe-xat.%Ga alloys, an underlying inhomogeneity from Ga atoms embedded into the α-Fe matrix was believed to be the origin of giant magneostrictive properties. I have systematically investigated the phase structure and nano-size heterogeneity of Fe-xat.%Ga alloys subjected to different thermal treatments using standard TEM and high resolution TEM for 10Ph. D.

During the last few decades, interest in gas hydrates has been increasing significantly because of their economic potential as future energy source and their potential role in geohazards and global climate change. The global climate change is a particularly sensitive issue for the Polar Regions, such as Antarctica. In the South Shetland margin (Antarctic Peninsula), the occurrence of a potential gas hydrate reservoir has been demonstrated from the analysis of geophysical data acquired during three Italian Antarctic cruises. In order to enhance the knowledge of gas hydrate systems, I analyzed Ocean Bottom Seismometer (OBS) and coincident multi-channel seismic (MCS) data acquired in 2004. The main objectives of this thesis are to estimate the distributions and concentrations of gas hydrate and free gas within the sediments, and to investigate the system’s petrophysical properties. Travel time inversion and forward modeling of OBS data were performed to estimate detailed P- and S-wave velocity fields. The P-wave velocity field was determined by the inversion of refractions and reflections in OBS data, while the S-wave velocity field was obtained by ray-tracing forward modeling of the converted S-waves from the horizontal components of OBS data. Several velocity models were tested in order to reduce the errors caused by the spatial drift of the OBS from the MCS line during sinking, and the errors from inversion. The final velocity model shows that P-wave velocity increases gradually with depth down to the bottom simulating reflection (BSR) at approximately 510-650 m below the seafloor. The layer with high P-wave velocity of 2.0-2.1 km/s just above the BSR can be associated with the presence of gas hydrates. Below the BSR, a low velocity layer of 1.4-1.6 km/s is observed, which indicates the presence of free gas. From the analysis of critical refractions in OBS data, the base of free gas layer (BGR) occurs at a depth varying between 80-160 m below the BSR. Forward modeling of converted S-waves in OBS data allows us to obtain Poisson’s ratio estimates. We observe that Poisson’s ratios are fairly uniform within each layer and they show good agreement with previous study performed in this area. The comparison of Poisson’s ratio indicates that the gas hydrate reservoir shows no significant regional variations. The resulting velocity fields were translated in terms of gas hydrate and free gas concentrations, using a modified Biot-Geerstma-Smit theory. The results show that hydrate concentration in the layer just above the BSR ranges from 10% to 15% of total volume, and free gas concentration is approximately 0.3% to 0.8% of total volume assuming a uniform gas distribution. Part of this research related to the OBS analysis and gas-phase estimation, has been published in the international journal Energies (Song et al., 2018) and included in the Appendix 1.

This thesis extends the concept of compactifications of topological spaces to a setting where spaces carry a partial order and maps are order-preserving. The main tool is a Stone-type duality between the category of d-frames, which was developed by Jung and Moshier, and bitopological spaces. We demonstrate that the same concept that underlies d-frames can be used to do recover short proofs of well-known facts in domain theory. In particular we treat the upper, lower and double powerdomain constructions in this way. The classification of order-preserving compactifications follows ideas of B. Banaschewski and M. Smyth. Unlike in the categories of spaces or locales, the lattice-theoretic notion of normality plays a central role in this work. It is shown that every compactification factors as a normalisation followed by the maximal compactification, the Stone-Cech compactification. Sample applications are the Fell compactification and a stably compact extension of algebraic domains.

Diagramme de phase et donnees thermodynamiques du systeme ternaire as-ga-in sont optimises a partir des valeurs experimentales disponsibles. Etude de l'influence de l'energie elastique sur le diagramme de phase. Analyse thermodynamique de l'epitaxie par jets moleculaires des multicouches in#1##yga#yas

碩士
國立成功大學
材料科學及工程學系碩博士班
94
Eutectic Sn-Pb solder are mainly used to connect the electronic devices and printed circuit board. But, many countries have concerned about lead, which would pollute environment and hurt human health. The development of lead-free solders has become the most important issue, oxidation resistance, wettability, and other properties. This study investigated Sn8.5Zn0.5Ag0.01Al0.1Ga solder balls, which was developed by our lab. This study investigated the micro-structure of solder balls under electromigration and thermomigration effects. After assembly, we would apply different of current density to solder balls at 120℃. Electrons would impact the intermetallic compounds (AuZn3 and AgZn3) seriously in current crowding section. The intermetallic compounds would decompose. The atoms coming from intermetallic compound decomposition would move in the direction of temperature gradient and react to form intermetallic compounds. Without other atom to occupy the site in which intermetallic compounds decomposed, it would be observed voids. If the directions of thermomigration and electromigration were the same, Sn atom would be affected seriously by temperature gradient and electric impaction, and move in the direction. In this lead-free solder, the AgZn3-AuZn3-AgZn3 three layers compound would transfer and consume the Zn-rich phase in solder balls.

碩士
國立成功大學
材料科學及工程學系碩博士班
95
The Sn-Zn based solder exhibits unsatisfactory oxidation resistance. It is very prone to oxidation that decreases the life of products. This study investigated the oxidation behavior of Sn-8.5Zn-xAg-0.01Al-0.1Ga(x= 0~1.0wt％) solders at high temperatures and during heat/humidity exposure. During the experiment, some whiskers formed on the surface of the solder. Therefore, the observation of Sn whisker growth behavior was also investigated in this study. The microstructure of Sn-8.5Zn-xAg-0.01Al-0.1Ga(x=0~1.0wt％) shows that the AgZn3 compound was formed after the addition of Ag to the solder. The results of thermal gravimetric analysis(TGA) showed that the oxidation rate and oxide decreased as the Ag content of Sn-8.5Zn-xAg- 0.01Al-0.1Ga(x=0~0.5wt％) increase. The major composition of the oxide was ZnO. Because the oxidation layer blocked the reaction and diffusion between Zn and O2, the oxidation reaction reaches saturation after 25 minutes. The content of Zn-rich phase decreased in the matrix. After heat/humidity exposure at 85℃/85％RH(relative humidity), the major oxide formed are ZnO and a few SnO2. The thickness of oxidation layer increases with increasing Ag content. Sn whisker growth was driven by the compressive stress in the solder. The compressive stress is introduced due to the volume expansion when ZnO formed at the grain boundary of Sn.

碩士
國立清華大學
材料科學工程學系
103
In this study, zinc sulfide thin films are prepared by ammonia-free chemical bath deposition that we can find out the useful parameters applying to CuIn1-xGaxSe2 thin film solar cell. Use the zinc sulfate and thioacetamide (TAA) to be the sources of zinc ions and sulfur ions, respectively. In contrast to conventional process, adding ammonia as a complexing agent. Fabrication of ammonia-free also without any complexing agents CBD-ZnS buffer layer for CIGS was attempted. The total thesis can divide into three parts to optimize the ammonia-free CBD-ZnS buffer layer devices. The first part: A novel chemical approach that applied at room temperature to clean and passivate at the same time surface of CIGSe absorber before buffer layer deposition. By pre-treatment on CIGS surface with TAA acidic solution, oxides can be removed and additional S-containing layer forms, inducing remarkable enhancement in the electrical performances of the CIGS solar cells. The second part: the deposition times are controlled. we can fabricate an ultrathin also less Zn(OH)2 formation ZnS thin film by ammonia-free CBD process to form a rigid p-n heterojunction ; Also, light soaking is not needed in this process to optimize photovoltaic performance.The X-ray photoelectron spectroscopy (XPS) is used and measured that indicating the ZnS thin films formed by ammonia-free process revealed higher sulfur-to-oxygen ratio than ammonia process one. 30 minutes is choose for the ideal reaction time. The efficiency 9.16% was achieved without light soaking treatment. The third part: After ammonia-free CBD-ZnS buffer layer deposition, two different kinds of post-treatment are investigated. By post air-annealing, zinc may diffusion into bulk CIGS that result in the formation of buried p-n homo-junction, significantly improved cell performaces from 1.28% to 9.16%. With extra oxygen plasma treatment, higher sulfur-to-oxygen ratio ZnS thin film obtained by ammonia process may be reduced. Further, combined both oxygen plasma treatment with the post air-annealing, devices using ammonia-free CBD-ZnS buffer layer can reach 10.16%, which is almost the same as that of the cells pepared by ammonia process with 60 minutes light soaking treatment.

Im binären Mn-Ga-System wurde für Legierungen mit 55 at.% bis 65 at.% Mangan die Phasenbildung der L10-Phase mit Röntgenbeugung und Differenzialkalorimetrie untersucht. Nach der Herstellung der L10-Phase in allen Legierungen erfolgte eine Untersuchung der intrinsischen magnetischen Eigenschaften. Die Mn55Ga45-Legierung zeigte dabei die höchste Sättigungsmagnetisierung mit µ0Ms = 0,81 T. Für diese Legierung erfolgten deshalb Versuche zur Verbesserung der extrinsischen Eigenschaften. Dazu wurden Pulver gemahlen und die Möglichkeit der Ausrichtung im Magnetfeld untersucht. Dabei konnte ein Texturgrad von 0,45 für Pulver mit einer Partikelgröße kleiner 10 µm erreicht und die Koerzitivfeldstärke um das 7-fache gegenüber der Volumenprobe erhöht werden. Weiterhin konnten die Pulverproben durch Heißkompaktieren bei 400 °C erneut zu einer Volumenprobe gepresst werden. Die dabei erhaltene Probe besitzt eine Koerzitivfeldstärke von 0,16 T und eine leicht reduzierte Sättigungsmagnetisierung auf Grund einer Packungsdichte von 83 %. Im ternären Mn-Al-Ga-System wurden Proben der Sollzusammensetzung Mn55Al45-xGax mit 5,625 < x < 22,5 hergestellt. Für Legierungen mit x >= 11,86 erwies sich eine Wärmebehandlung bei 600°C für 24 Stunden als ausreichend die reine L10-Phase zu erzeugen. Bei den Legierungen mit einem geringeren Ga-Anteil war eine zweistufige Wärmebehandlung notwendig, um ausschließlich L10 zu erhalten. Nach der ersten Wärmebehandlung bei 1100 °C entstand ein Phasengemisch aus gamma2 und L10(epsilon). Letzteres wurde aus der epsilon-Hochtemperaturphase gebildet. Durch die anschließende Wärmebehandlung bei 500 °C für 24 Stunden konnte die verbleibende gamma2-Phase in L10(gamma2) umgewandelt werden. Untersuchungen der lokalen Legierungszusammensetzung ergaben einen geringeren Mn-Anteil der L10(gamma2)-Phase im Vergleich zu L10(epsilon). Die Unterschiede in den zwei L10-Phasen konnten weiterhin durch eine Reflexaufspaltung in den Röntgenbeugungsaufnahmen sowie der Existenz zweier Curie-Temperaturen bestätigt werden. Die gemessenen Sättigungsmagnetisierungen ergaben eine Superposition beider Phasen und einen maximalen Wert von µ0Ms = 0,85 T. Untersuchungen der thermischen Stabilität der L10-Phasen bei 700 °C zeigten, dass die L10(gamma2)-Phase thermisch stabil ist und sich die L10(epsilon)-Phase langsam in beta-Mn und gamma2 zersetzt. Bei der Zersetzung war im Vergleich zum binären Mn-Al-System eine starke Steigerung der thermischen Stabilität durch die Substitution geringer Mengen Galliums zu erkennen. Über die zersetzungsbedingte Reduktion der Magnetisierung konnten Abschätzungen der Zersetzungskinetik getroffen werden.

The provision of free basic water for domestic uses and a more equal distribution of water for productive uses are seen as important instruments to redress inequities from the past and eradicate poverty in South Africa (SA). Although the government committed itself to providing free basic water for all, this result is still far to be reached, particularly in rural areas. Financing of multiple use water services was identified as an important ingredient to insure improved access to water for rural poor in SA and at the same time allow productive uses and broaden livelihood options. Recent evidence indicated the potential contribution that productive uses of domestic water might make to food security and poverty reduction in rural areas of SA. Following the principles of integrated water resource management (IWRM), efficient, equitable and sustainable investment in improved water services should be demand driven, that is, it should be based on a thorough understanding of effective demand by consumers for multiple use water services. The assessment of demand for improved water services provides the basis for micro level analysis of consumer benefits from multiple water uses. Such studies are not common in SA’s rural areas, where most of the economic analyses focus on either domestic or irrigation water demand. This study attempts to fill this gap by assessing the household demand for multiple use water services in Sekororo-Letsoalo area in the Limpopo Province. Choice modelling is the approach used to identify the attributes determining demand for water services and quantify their respective importance. Households are presented with alternative sets of water services, corresponding to different levels of the attributes. In this study, the following attributes were used: water quantity, water quality, frequency of water supply, price of water, productive uses of water, and source of water. Choice modelling allows estimating the relative importance of these attributes for various strata of the studied population, and ultimately provides a measure of the willingness to pay for different aspects of water demand (attributes), including productive water uses. Results show that households in rural areas are willing to pay for water services improvements. Due to the poor quality of present water services in the area, users are primarily concerned with basic domestic uses and demand for non domestic water uses is low. Only households already relatively well served are interested in engaging in multiple water uses.
Dissertation (MSc(Agric))--University of Pretoria, 2009.
Agricultural Economics, Extension and Rural Development
unrestricted

碩士
國立成功大學
材料科學及工程學系碩博士班
95
This research used the Sn-9Zn lead-free solder alloy add the third element Ga in different content ( 0.4 , 0.6 , 0.8 wt . % ) and Ge ( 0.3 , 0.4 , 0.5 wt . %) separately to investigate the effects of adding Ga and Ge on the anti-oxidation and tensile behavior of Sn-9Zn lead-free solder alloy. The experimental results revealed that the microstructure of Sn-9Zn-xGa alloys after oil bath heat treatment at 120℃ for 2hr, with increasing the Ga content , the fraction of the irregular region formed with the coarse Zn particles arranged irregularly and β-Sn increased ; the fraction of the regular region formed with the aligned acicular Zn particles and β-Sn decreased. The microstructure of Sn-9Zn-xGe alloys after oil bath heat treatment at 120℃ for 2hr revealed that besides the pre-eutectic Zn and Sn-Zn eutectic region, there were deep gray Ge phase. The amount and the size of the Ge phase increased with increasing the Ge content. On the respect of the solid state surface oxidation, the oxidation occur on the surface of S9ZA, 0.4GaA and 0.4GeA were ZnO and few SnO2. Because the Ga was dissolved in both Sn and Zn phases and the activity decreased , the adding of Ga improved the oxidation of Sn-9Zn without any heat treatment. However, in the situation of the heat treatment at 120℃ in the air for 2hr, the oxide films on the surface were not easy formed to protect the base metal, the thickness of the oxide layer increased greatly. Because Ge segregated in the grain boundary and hindered the diffusion of Zn2+, the oxide layer was reactively thin. In the situation of the heat treatment at 120℃ in the air for 2hr, because the ZnO on the surface to protect the base metal, the thickness of the oxide layer didn’t increase. On the respect of the solidify surface oxidation, the experimental results revealed that S9ZR, 0.4GaR, 0.4GeR which were reflowed at 260℃ for 15min and cooled at RT , 5 times, there were ZnO on the surface and no tin oxides. When solidifying, because the Ga was dissolved in both Sn and Zn phases and hindered the diffusion of ions of metals .It caused the time of forming the zinc oxides on the surface increased and the zinc oxides became thick. About the adding of Ge, because Ge was not dissolved in both Sn and Zn phases, the zinc oxides formed on the surface quickly, and after solidifying the Ge segregated in the grain boundary and hindered the diffusion of Zn2+, the oxide layer was thinner than S9ZR. There was dynamic recrystalization phenomenon in the Sn-9Zn-xGa and Sn-9Zn-xGe tensile test at RT and 120℃. On the respect of tensile deformed resistance, because the solid solution effect, the tensile deformed resistance increased with increasing of Ga content at room temperature and the solid solution effect slight improved the tensile deformed resistance at high temperature (120℃). About the adding of Ge, because the Ge segregated in the grain boundary and the Ge phase improved the tensile deformed resistance but didn’t increase obviously with increasing Ge content. There was no help at all on tensile deformed resistance by adding Ge at high temperature (120℃).

碩士
國立臺灣科技大學
材料科學與工程系
104
In recent years, confronting with the problem of energy crisis, Cu(InGa)Se2 or CIGSe thin-film solar cells are gradually getting researchers’ attentions. In this field, solar cell device almost uses CdS as a buffer layer and ZnO as a n type one. Because CdS is toxic, GaN and InGaN in this work have been taken to replace CdS/ZnO for designing different solar cell structures. In the study, CIGSe precursor thin films were prepared by sputtering, followed by selenization with different annealing temperatures. The characterizations of thin films were analyzed by field-emission scanning electron microscopy (FE-SEM) epuipped with an energy dispersive X-ray spectrometer (EDS), X-ray diffractometry (XRD), and Hall measurement. Different Indium contents for InxGa1-xN that were used as n type layers for solar cell devices were also prepared by sputtering. The performance of the devices was then evaluated under the standard AM 1.5 illumination. The results showed that CIGSe thin films after made by co-sputtering and a two-step selenization process at 600oC had better surface morphology with the grain size of 1.0 – 1.5 m. FE-SEM, XRD and EDS analyses demonstrated that the films were single phase with the close component of CuIn0.7Ga0.3Se2 even selenization at different temperatures. Then, InxGa1-xN thin films made by RF sputtering replaced CdS as the buffer layer for the solar cell structure. CdS-free CIGSe/In0.15Ga0.85N/ZnO solar cell with the structure I had the best conversion efficiency of 1.04% conversion, while it was 3.07% for the traditional CIGSe/CdS/ZnO solar cell structure.

碩士
國立中正大學
化學工程研究所
103
With the development of miniaturization in electronic products, ENIG has been regarded as a surface treatment in recent years. The black pad problem was usually occur in ENIG technique and Ni will dissolve into the solder under electron current stressing, the electroless Pd can solve the black pad problem and has better wettability. In this research, we thickened Pd layer and investigated inhibition of electromigration failure by introducing PdSn4 layer in lead-free solder joints. Originally the reaction was formed PdSn4 phase, but Ni was dissolved in the reflow process. So PdSn4 phase was transformed into NiSn4 phase. When the reaction time reached to 4 days, the reaction phase is as the same as solid/solid reaction at the interface 1. At the interface 2, the Ni3Sn4 phase was formed. Because of the fast consumption of Ni substrate, voids exist at the irregular interface 2 and a lot of NiSn4 phase was drifted to the Sn solder. This result was similar to the previous electromigration study on the Sn/Ni system. Therefore, using thin Pd layer could not retard Ni diffusion either. As the thickness of Pd layer increased to 3μm, the layered structure NiSn4 phase was maintained when the reaction time reached to 5 days. But when reaction time increased to 10 days, much Ni substrate was consumed. The enough Pd content can be difficult to be affected by the current stressing but was easily affected by the Ni substrate, so this study used Cu layer to protect the Pd layer. When reaction time reached to 10 days, the reaction phase, PdSn4, remained layered structure. However, when it converted to NiSn4 phase, the Ni atoms were migrated into the Sn solder by interstitial diffusion and grain boundary diffusion. In summary, the PdSn4 phase was a good diffusion barrier. The Pd plating has a significant impact on the solder joints. In the second part, we studied the solid/solid and liquid/solid reactions between the trace added Ga solder and Cu or Ni substrate. For solder within low concentration of Ga, the reaction phase did not change. When the Ga concentration increased, its reaction phase was converted to Cu-Ga and Ni-Ga phase which had good inhibitory in the initial reaction period, but when reaction time increased, the phase was converted to Cu-Sn and Ni-Sn phase. At that time, there was no suppression effect on the reaction rate. At the Ag (10μm)/Cu case, the reaction phase was dissolved at the interface quickly during liquid/liquid reaction. During the solid/solid reactions, the Ag3Sn phase which can do a diffusion barrier was formed at the interface. In Co and Pd case, liquid/solid and solid/solid reaction, the CoSn3 phase was formed when the solder has low concentration of Ga. With the concentration of Ga increasing, the CoSn3 phase generation rate decreased. For higher concentrations of Ga, the CoSn3 phase was transformed into the CoGa phase and the reaction rates were extremely slow. When changing into the Pd substrate, the PdSn4 phase was formed in the reactions and the reaction rate of the PdSn4 phase decreased with the concentration of Ga increasing. These results suggested that Ga in solder had bad suppressed IMC effect at the Cu and Ni substrate, but had good suppression effect at the Co and Pd substrate.

Text in English with abstracts in English, Sepedi and Venda
Access to firewood and other affordable energy sources is essential to the livelihoods of rural households in developing countries. Studies have been conducted to understand the reasons behind an extensive reliance on firewood in rural areas, especially in developing countries, despite improved electrification rates and a number of government policies introduced to encourage rural households to switch from traditional to modern fuels. This study aimed at assessing and thus understand the factors influencing the use of firewood by households in Ga - Malahlela village in Limpopo Province. Limited research has been conducted on firewood use, subsequent to improved electrification in rural areas in South Africa, hence it was to shed light on this little-explored subject on which the study was carried out. The assessment was based on household demographics and household energy use patterns, with a structured questionnaire being utilised to arrive at a detailed understanding of the factors that drive firewood use. It was established that firewood was still used to a significant degree, to satisfy household energy needs such as cooking, water heating and space heating. This was mainly due to the socioeconomic status of households. Socio-economic factors such as income, education level, household size and preference were found to be the factors exerting the greatest influence on the use of firewood among households in the study area. Psychological variables and the geographical location of the study area were also shown to promote the use of firewood. The study further revealed that, as indicated in the reviewed literature, households in the study area fuel stack and do not ascend the energy ladder. The reviewed literature further indicated that not all factors have equivalent significance in determining the behaviour and pattern of household energy use. This indicates that energy sources such as firewood are not completely discarded but are instead used in conjunction with modern energy sources such as electricity. In conclusion, this study established that despite the availability of electricity, as a result of poverty and the lack of free basic services such as free basic electricity, reliance on firewood in rural areas will continue.
Go hwetša dikgong le methopo ye mengwe ya dibešwa tšeo di rekegago go bohlokwa go mekgwa ya malapa a dinagamagaeng go hwetša dilo tše bohlokwa tša bophelo dinageng tšeo di hlabologago. Dithutelo di phethagaditšwe go kwešiša mabaka ao a thekgago kholofelo go dikgong mafelong a dinagamagaeng a dinaga tšeo di hlabologago le ge go na le ditekanyo tše di kaonafaditšwego tša tlhagišo ya mohlagase le palo ya melaotshepetšo ya mmušo yeo e tsebišitšwego go tutuetša malapa a dinagamagaeng go fetoga go tloga go dibešwa tša sekgale go iša go tša sebjale. Thutelo ye e ikemišeditše go lekola ka gona go kwešiša mabaka ao a huetšago malapa a Motsaneng wa Ga-Malahlela ka Profenseng ya Limpopo go diriša ya dikgong. Dinyakišišo tše lekantšwego di phethagaditšwe ka ga tirišo ya dikgong ka morago ga tlhagišo ya mohlagase yeo e kaonafaditšwego mafelong a dinagamagaeng ka Afrika Borwa, gomme e be e swanetše go fa tshedimošo ka ga hlogotaba yeo e hlohlomišitšwego gannyane gore thutelo ye e phethagatšwe. Tekolo ye e theilwe go dipalopalo ka ga malapa setšhabeng le mekgwa ya malapa ya go dirišwa dibešwa, ka go diriša lenaneopotšišo leo le beakantšwego gore go fihlelelwe kwešišo ye e hlalošago ka botlalo mabaka ao a hlohleletšago tirišo ya dikgong. Go lemogilwe gore dikgong di sa dirišwa ka bontši bjo bo bonagalago go kgotsofatša dinyakwa tša malapa tša enetši tše bjalo ka go apea, go ruthetša meetse le go ruthetša lefelo. Se se be se swanela gagolo ka lebaka la boemo bja ka moo ekonomi e amago tšwelopele ya malapa. Mabaka a ka moo ekonomi e amago tšwelopele ya setšhaba a go swana le ditseno, boemo bja thuto, bogolo bja lelapa le tšeo di ratwago go hweditšwe go ba mabaka ao a hlohleletšago khuetšo ye kgolokgolo go tirišo ya dikgong gare ga malapa thutelong ye. Dielemente tšeo di ka fetolwago le lefelo tikologong ye e itšeng tša thutelo le tšona di bontšhitšwe go godiša tirišo ya dikgong. Thutelo ye gape e utollotše gore, bjalo k age go šupilwe dingwalong tšeo di lekotšwego, malapa a lefelong la thutelo a latela mekgwa ya dibešwa tša mehutahuta gomme ga a latele manamelo a enetši. Dingwalo tšeo di lekotšwego di laeditše go ya pele gore ga se mabaka ka moka ao a nago le bohlokwa bjo bo lekanago go šupeng boitshwaro le mokgwa tša tirišo ya enetši ka malapeng. Se se šupa gore methopo ya enetši ye bjalo ka dikgong ga se ya tlogelwa ka gohlegohle eupša e dirišwa mmogo le methopo ya sebjale ya enetši ye bjalo ka mohlagase. Go ruma, thutelo ye e utollotše gore le ge go na le mohlagase, ka lebaka la bohloki le tlhaelo ya ditirelo tša motheo tša mahala tše bjalo ka mohlagase wa motheo wa mahala, kholofelo go dikgong dinagamagaeng e tlo tšwela pele.
U swikelela khuni na zwiṅwe zwiko zwa fulufulu zwine zwa swikelelea ndi zwa ndeme kha u tsireledza zwo teaho zwa vhutshilo kha miṱa ya vhupo ha mahayani kha mashango o no khou bvelelaho. Ngudo dzo farwa u itela u pfesesa zwiitisi zwa u ḓitika zwihulwane nga khuni kha vhupo ha mahayani kha mashango ane a khou ḓi bvelela zwi si na ndavha na u khwiniswa ha u dzheniswa ha muḓagasi na tshivhalo tsha mbekanyamaitele dza muvhuso dzo ḓivhadzwaho u ṱuṱuwedza miṱa ya vhupo ha mahayani u bva kha u shumisa zwivhaswa zwa kale u ya kha zwa ano maḓuvha. Ngudo iyi yo livhiswa kha u asesa na u pfesesa zwiṱaluli zwine zwa ṱuṱuwedza u shumiswa ha khuni nga miṱa ya Muvhunduni wa Ga-Malahlela Vunduni ḽa Limpopo. Ṱhoḓisiso dzi si nngana dzo itwa nga ha u shumiswa ha khuni hu tshi tevhela u dzheniswa ha muḓagasi vhuponi ha mahayani Afurika Tshipembe, ho vha u bvisela khagala nga ha zwiṱuku zwo wanululwaho kha thero heyi ye ngudo ya i bveledzisa. U linga ho vha ho ḓisendeka nga ngudamirafho ya miṱa na kushumisele kwa fulufulu miṱani, hu na mbudzisombekanywa dzo dzudzanywaho dzo shumiswaho u swikelela kha u pfesesa nga vhuḓalo zwiṱaluli zwine zwa ta u shumiswa ha khuni. Ho dzhielwa nṱha uri khuni dzi kha ḓi shumiswa nga maanḓa u ḓisa ṱhoḓea dza fulufulu miṱani u fana na u bika, u vhilisa maḓi na u dudedza vhudzulo. Hezwi zwo tea nga maanḓa kha vhuimo ha matshilisano a zwa ikonomi miṱani: zwiṱaluli zwa ikonomi ya matshilisano zwi ngaho sa mbuelo, vhuimo ha pfunzo, vhuhulu ha muṱa na zwo no takalelwa ho wanwa uri ndi zwiṱaluli zwine zwa shumisa ṱhuṱhuwedzo khulwane ya u shumiswa ha khuni vhukati ha miṱa ya vhupo ha ngudo. Variabuḽu dza saikhoḽodzhikhaḽa na vhupo ha ḓivhashango zwa vhupo ha ngudo zwo sumbedziswa u ṱuṱuwedza u shumiswa ha khuni. Ngudo yo isa phanḓa na u wanulusa uri, sa zwo sumbedziswaho kha maṅwalwa o sedzuluswaho, miṱa kha vhupo ha ngudo i kuvhanganya fulufulu ngeno hu sina u gonya ha tshanduko ya kushumisele kwa fulufulu. Maṅwalwa o sedzuluswaho o sumbedzisa a tshi i sa phanḓa uri a si zwiṱaluli zwoṱhe zwine zwa vha na ndeme i linganaho kha u ta vhuḓifari na kushumisele kwa fulufulu miṱani. Hezwi zwi sumbedza uri zwiko zwa fulufulu zwi ngaho sa khuni a zwo ngo laṱelwa kule tshoṱhe fhedzi zwi shumiswa zwo ṱanganyiswa na zwiko zwa fulufulu zwa ano maḓuvha zwi ngaho sa muḓagasi. Ri tshi pendela, ngudo iyi i ta uri na musi muḓagasi u hone, nga nṱhani ha vhushayi na ṱhahelelo ya tshumelo dza muḓagasi wa mahala wa mutheo u fana na muḓagasi wa mahala wa mutheo, u ḓitika nga khuni vhuponi ha mahayani hu ḓo ḓi bvela phanḓa.
Department of Environmental Science
M.A. (Environmental Science)