Cette dissertation présente les résultats des mesures des sections efficaces inclusives de production des particules chargées légères (protons, deutons, tritons, 3He, alpha, 6Li, 7Li et 7Be) ainsi que les multiplicités neutroniques associées, relevés lors des réactions nucléaires induites par protons et alpha sur une cible de natSi. Ces mesures ont été réalisées auprès du cyclotron CYCLONE de Louvain-la-Neuve aux énergies de 26.5, 48.5 et 62.9 MeV pour les réactions (p, (nat)Si) et de 25.4, 45.5 et 57.8 MeV pour les réactions (alpha, (nat)Si). Le système de détection, original dans sa conception, a été assuré par 15 télescopes constitués d'un assemblage de jonctions silicium et de scintillateurs inorganiques CsI assurant une couverture angulaire de 0 à 360°. Toutes les particules chargées étudiées dans ce travail ont été identifiées sur base de l'information de leurs pertes d'énergie dans les différentes jonctions et par la technique de l'analyse en forme des signaux lumineux issus des CsI. La détection des neutrons a été assurée par le multi-détecteur à neutrons DEMON constitué de 81 scintillateurs organiques liquides. Ces neutrons ont été identifiés par la technique de l'analyse en forme du signal lumineux. L'énergie des neutrons a été déduite par mesure de leur temps de vol. Les distributions angulaires des pics élastiques et inélastiques de la diffusion des protons et des alpha sur le 28Si ont été confrontées aux prédictions des modèles Optique, DWBA et Canaux Couplés, utilisant différents potentiels optiques. Une comparaison des résultats expérimentaux avec ceux déjà publiés sur des réactions similaires ou comparables a également fait l'objet de ce travail. De plus, les résultats ont été confrontés à ceux des prédictions des codes de simulation GNASH et TALYS. Une attention particulière a été portée aux prédictions du code TALYS. Enfin, ce travail fournit une très large et très complète base de nouvelles données expérimentales qui constitue un atout majeur et bénéfique aussi bien dans l'amélioration des codes théoriques de simulation de ce type de réactions que dans les prédictions des dégâts radiatifs induits par les différents rayonnements ionisants dans les semi-conducteurs, en général, et les composants électroniques, en particulier.

Cette dissertation présente les résultats des mesures des sections efficaces inclusives de production des particules chargées légères (protons, deutons, tritons, 3He, alpha, 6Li, 7Li et 7Be) ainsi que les multiplicités neutroniques associées, relevés lors des réactions nucléaires induites par protons et alpha sur une cible de natSi. Ces mesures ont été réalisées auprès du cyclotron CYCLONE de Louvain-la-Neuve aux énergies de 26.5, 48.5 et 62.9 MeV pour les réactions (p, (nat)Si) et de 25.4, 45.5 et 57.8 MeV pour les réactions (alpha, (nat)Si). Le système de détection, original dans sa conception, a été assuré par 15 télescopes constitués d'un assemblage de jonctions silicium et de scintillateurs inorganiques CsI assurant une couverture angulaire de 0 à 360°. Toutes les particules chargées étudiées dans ce travail ont été identifiées sur base de l'information de leurs pertes d'énergie dans les différentes jonctions et par la technique de l'analyse en forme des signaux lumineux issus des CsI. La détection des neutrons a été assurée par le multi-détecteur à neutrons DEMON constitué de 81 scintillateurs organiques liquides. Ces neutrons ont été identifiés par la technique de l'analyse en forme du signal lumineux. L'énergie des neutrons a été déduite par mesure de leur temps de vol. Les distributions angulaires des pics élastiques et inélastiques de la diffusion des protons et des alpha sur le 28Si ont été confrontées aux prédictions des modèles Optique, DWBA et Canaux Couplés, utilisant différents potentiels optiques. Une comparaison des résultats expérimentaux avec ceux déjà publiés sur des réactions similaires ou comparables a également fait l'objet de ce travail. De plus, les résultats ont été confrontés à ceux des prédictions des codes de simulation GNASH et TALYS. Une attention particulière a été portée aux prédictions du code TALYS. Enfin, ce travail fournit une très large et très complète base de nouvelles données expérimentales qui constitue un atout majeur et bénéfique aussi bien dans l'amélioration des codes théoriques de simulation de ce type de réactions que dans les prédictions des dégâts radiatifs induits par les différents rayonnements ionisants dans les semi-conducteurs, en général, et les composants électroniques, en particulier.

The objective of the thesis is to fabrication an optical demultiplexer using Thin-film filter(TFF) based on Si-bench technology. The advantage over conventional bulk-optics technology in fact that the active alignment is performed in only 1-dimension. There fore the cost of package of the demultiplexer can be reduced significantly. Lights at multiple wavelengths were launched into the demultiplexer through a Dual-core single mode fiber(SMF). Due to the wavelength selection of the TFF, only the designate wavelength can pass through the filter and is refocused by the C-lens to the output Single-core single mode fiber(SMF). The other wavelengths will be reflected by the TFF, pass through the Grin-lens again and return to the Dual-core single mode fiber(SMF). The measured reflection(1470nm¡B1490nm¡B1510nm¡B1530nm¡B1550nm) and transmission (1470nm¡B1490nm¡B1510nm¡B1530nm)lasers of the lights are around 0.5dB.

Thesis (Master)--Guo li Zheng zhi da xue, 1981.

English Abstract In this thesis, we investigate the electrical properties and reliabilities of poly-Si TFTs for system on panel application. Roughly, we divide the thesis into two parts, n-type and p-type TFTs respectively. In n-type TFT, we mainly study degradation characteristics of TFTs under dynamic stress. On the other hand, we focus on special negative bias temperature instability (NBTI) degradation for p-type poly-Si TFTs. Because grain boundary in poly-Si film and serious self-heating effect due to glass substrate, which has a poor thermal conductivity, the electrical properties and reliabilities of poly-Si TFTs become more complicated, compare with metal-oxide-semiconductor field effect transistor (MOSFET). Therefore, in the thesis, we found some strange phenomena never observed in a-Si TFT and MOSFET. In chapter 3, the degradation mechanism of n-channel poly-silicon thin film transistor (poly-Si TFT) has been investigated at room temperature under dynamic voltage stress, which simulate under high frequency operation as driving devices. The ON-current of TFT is degraded to as low as 0.3 times of the initial value after 1000 second stress. On the other hand, both the sub-threshold swing and threshold voltage kept well during the AC stress. The current crowding effect was rapidly increased with increasing of stress duration. However, comparing the initial and degraded characteristics at rising temperature, namely, 150◦C, the ON-current of TFT only decrease to 75 percent of the initial value after 1000 second AC stress. It depicts that creation of effective trap density in tail-states of poly-Si film is responsible for the electrical degradation of poly-Si TFT. At high temperature, electron has enough energy to pass the energy barrier created by ac stress and the degradation is less obvious. In chapter 4, the degradation mechanism of n-channel poly-silicon thin film transistor (poly-Si TFT) has been investigated under dynamic voltage stress, which simulate under low frequency operation as pixel switches. Surprisingly, two totally different degradations of TFTs were observed after dynamic stress. Firstly field-effect mobility and driving current increased during early stress. However, a clear and rapid degradation of field-effect mobility occurred instead during later stress. Additionally, the threshold voltage of stressed TFTs strangely shifted to negative direction in later stress, which was never observed in early stress. Finally, we clarify the degradation mechanisms for early and later stress respectively by varied temperature experiments. In chapter 5, the characteristics of p-type poly-silicon thin film transistor (poly-Si TFT) with dynamic bias stress were investigated. The AC stress is operated with the constant drain voltage (15V) and the varying gate voltage (0V~-15V) to degrade the devices. There are some phenomena which cannot be completely explained by typical NBTI mechanism in the experiment. In addition to NBTI, we suggest that the self-heating effect might be involved, because the self-heating effect could rise channel temperature and cause the dissociation of the Si-H bonds at the poly-Si/SiO2 interface due to the Joule heating. The released hydrogen reacts with SiO2 and causes the fixed charge in the gate oxide. Thus, the degradation of electrical characteristics of device is mainly dominated by the self-heating induced NBTI effect. In chapter 6, we investigate the asymmetric negative bias temperature instability degradation of poly-Si TFTs. Electric measurements of normal and reverse modes were employed to analyze the degradation on Vt, current, leakage current and sub-threshold swing (S.S.). The results indicated that a non-uniform vertical electric field at the poly-Si/SiO2 resulted in asymmetric negative bias temperature instability degradation. The trap generation was a grading distribution from source to drain. Moreover, some energy diagrams were proposed to explain the experimental data. Sequentially, asymmetric TFT degradation resulted from a grading distribution of trap state induced by asymmetric NBTI.

The objective of this research is to achieve high-efficiency, low-cost, commercial-ready, screen-printed Silicon (Si) solar cells by reducing material costs and raising cell efficiencies. Two specific solutions to material cost reduction are implemented in this thesis. The first one is low to medium concentrator (2-20 suns) Si solar cells. By using some optics to concentrate sunlight, the same amount of output power can be achieved with cell area reduced by a factor equal to the concentration ratio. Since the cost of optics is less than the semiconductor material, electricity price from the concentrator photovoltaics (PV) system is therefore reduced. The second solution is the use of epitaxially grown Si (epi-Si) wafers. This epi-Si technology bypasses three costly process steps (the need for polycrystalline silicon feedstock, ingot growth, and wafer slicing) compared to the traditional Si wafer technology and therefore reduces the material cost by up to 50% in a finished PV module. In addition, high efficiency Si solar cells with reduced metal contact recombination are studied and modeled by implementation of passivated contacts composed of tunnel oxide, n+ polycrystalline Si and metal on top of n-type Si absorber to reduce the cost ($/Wp) of PV module.

The purpose of this study is using titanium dioxide (TiO2) as gate oxide on thin film transistor (TFT) and discussed with their physical, chemical and electrical properties. Amorphous silicon (a-Si) and polycrystalline silicon (poly-Si) are used as substrates. The metal-organic chemical vapor deposition (MOCVD) and the liquid phase deposition (LPD) are used as the TiO2 growth methods. About the LPD growth method, ammonium hexafluoro-titanate ((NH4)2TiF6) and hexafluorotitanic acid (H2TiF6) are used as Ti sources. We are interested in two parts: (1) the growth mechanisms, physics properties, chemical properties and electrical properties of MOS structure; (2) the fabrication processes and electrical properties of devices. In the first part, we discuss the thin films characteristics on a-Si and poly-Si substrates. For the MOCVD growth method, the MOCVD-TiO2 film tends to form the poly structure. Poly structure has a higher dielectric constant, however, higher traps and dangling bonds also exist at the grain boundaries. Thus, poly structure of TiO2 film has a higher leakage current. For the LPD growth method, the film tends to form the amorphous structure. Amorphous structure has lower leakage current but also has lower dielectric constant. The film that grown from the (NH)2TiF6 source is called LPD-TiO2 film. The film that grown from the (NH)2TiF6 source is called LPD-TixSi(1-x)Oy film. Both films are incorporated with OH and F ions during the growth, the OH and F ions can be outgassed during the low temperature annealing process. In addition, appropriate F ions in the film can passivate the traps and dangling bonds. The low temperature treatments in N2 or O2 ambient and post-metallization annealing (PMA) are adopted to improve the film characteristics. On the other hand, the substrate is not a prefect structure (not a single structure). Thus the film may be influenced by substrate during the annealing treatment. In the second part, the electrical properties of TFT devices were discussed under the coplanar structure. There are several differences of the operation principle in TFT and MOSFET. A-Si and poly-Si are the un-doped substrates with many traps in the bulk. The channel should be occurred through the full depletion mode. The full depletion region is the substrate that under the gate electrode. Thus, the key point is kept the suitable thickness. Too thick, the channel can not appear. Too thin, the substrate may be over-etched. For ion implantation, due to the thinner active layer, the ion implantation energy should be lowed. In addition, the activation temperature and activation time should be adjusted suitable. We have fabricated the TFT devices with the MOCVD-TiO2 as gate oxide on poly-Si substrate. From the I-V characteristics, the Kink effect can be observed. However, the Ion/Ioff ratio is still low. We must further study how to increase the Ion/Ioff ratio.

The study of impurity diffusion in semiconductor hosts is an important field that has both fundamental appeal and practical applications. Ion implantation is a good technique to introduce impurities deep into the semiconductor substrates at relatively low temperature and is not limited by the solubility of the dopants in the host. However ion implantation creates defects and damages to the substrate. Annealing process was used to heal these damages and to activate the dopants. In this study, we introduced several species such as alkali metals (Li, Na, K), alkali earth metals (Be, Ca,), transition metals (Ti, V, Cr, Mn) and other metals (Ga, Ge) into semiconductor substrates using ion implantation. The implantation energy varies form 70 keV to 200 keV and the dosages vary between ~ 1.0x1012 and ~5.0x1015 atoms/cm2. The samples are annealed at different temperatures from 300°C to 1000°C and for different time intervals. The redistribution behaviors of the implanted ions are studied experimentally using secondary ion mass spectrometry (SIMS). We observed some complex distribution behaviors due to the defects created during the process of ion implantation. The diffusivities of some impurities are calculated and compared to previous data. It was found that the diffusivities of implanted impurities is related to the dosages, annealing temperatures and the defects and damages caused by ion implantation. Additionally, as we go from one type of semiconductor to another, the diffusion behavior of the impurities shows a different trend.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 59-62). / Wastewater treatment is a very energy intensive industry. Singapore has a state-of-the-art wastewater treatment system that uses a number of sustainable techniques that greatly improve its overall efficiency. The centralized Changi Water Reclamation Plant is one of the most advanced treatment facilities in the world. However, there are smaller, less efficient wastewater treatment plants still in use in Singapore. One of those is located in the Kranji Catchment region adjacent to the Lim Chu Kang Air Force Base. Called BJ725, this facility consists of a primary settler and a trickling filter. The purpose of this study is to determine the feasibility of using wind power, solar power, or methane gas combustion to meet the treatment facility's energy requirement. As the first part of this feasibility study, BJ725's energy requirement was analyzed. Additionally, wind and solar output was computed given historical meteorological conditions in Singapore, and the amount of power produced during methane gas combustion was computed given sludge output at BJ725. The outcome of these calculations showed mixed results. There was not one day of wind strong enough to produce usable energy in the 33-year meteorological dataset analyzed. Thus, there is essentially no potential for wind energy to be used in Singapore. Solar energy proved to be economically viable, but only with at least a 63 percent rebate. Sludge digestion and methane gas combustion proved to be by far the most economically viable option for wastewater treatment plants in Singapore. In the case of BJ725, approximately S$8,000 of yearly income can be generated if sludge digestion and methane gas combustion is utilized. Overall, sludge digestion seems to be the best option for wastewater treatment plants throughout the rest of the world. However, the three options studied are site specific and should be analyzed on a location-specific basis. / by Kevin John Foley. / M.Eng.