Tesis sobre el tema "Silicone hydrogel"

The thesis investigates the ocular response to silicone-hydrogel (SiH) contact lens wear, a relatively new contact lens material that has a higher modulus of rigidity and different surface coating than used in conventional hydrogel materials. The properties of SiH materials differ significantly from conventional hydrogels and, using subjective and objective means of assessment, the thesis examines how these properties affect reflection and biometry, ocular physiology, tear film characteristics, symptomatology, adverse events and complications. A range of standard and newly designed investigative techniques were employed, and latter involving novel imaging techniques, for the objective assessment of physiological changes which occur with contact lens wear. The study is the first to combine these techniques with biochemical analyses of the tear film composition. Forty-seven subjects were fitted with SiH lenses and randomly allocated to one of the two materials currently on the market (Lotrafilcon A or Balafilcon A) on an either daily or continuous wear basis. An additional control group of 14 age-matched non-contact lens wearers were monitored over the same period. Measurements were taken before and 1, 3, 6, 12 and 18 months after initial fitting. The findings reported in this thesis will enable contact lens practitioners and manufacturers to understand further the optical, physiological and biochemical nature of the ocular response to SiH contact lenses and hence facilitate the development of this important generation of contact lens material.

Silicone Hydrogel (SiHy) contact lenses are highly successful compared to previous soft lenses; they were developed to provide superior oxygen permeability. However, the hydrophobic natures of the silicone segments enhance lipid sorption which may diminish the lens surface wettability, clarity and comfort. While lens and lens care product are designed to remove lipid deposition, there is lack of experimental evidence to evaluate the actual performances with respect to lipid removal. An in vitro model using an artificial tear fluid containing radiolabeled lipids was employed in this thesis research to evaluate the efficacy of different multi-purpose lens care solutions in removing lipids from SiHy contact lenses. Additional rubbing with the lens care solution is often encouraged by professionals. Part of this research evaluated the effect of additional rubbing process on lipid removal. Overall, a multi-purpose solution (MPS) for lens care, Opti-Free PureMoist®, removed the most lipid deposition from lenses (senofilcon A, comfilcon A, and balafilcon A and one conventional hydrogel lens polymacon). The overall removal percentages were approximately 55% of DPPC and 28% of cholesterol from a conventional hydrogel. However, the MPSs did not remove lipids effectively from SiHy lenses. The highest percentages of removal were 3.08% of DPPC and 0.76% of cholesterol from SiHy lotrafilcon B lenses with Opti-Free PureMoist. The rubbing process increased the amount of removal in some MPSs, but the effects were small. The lack of removal of lipid suggests that the surfactants in the MPSs are not hydrophobic enough to remove lipids from SiHy lenses. Apparently a majority of deposited lipids absorbed into the lens matrix as rubbing did not enhance removal significantly. Future study on determining the concentration profile of lipid sorption throughout the lens thickness is encouraged. Another topic in this research thesis is the use of hydrogel lenses to deliver comfort agents or lubricating molecules from lenses. A screening study was performed in this research to select possible agents to be loaded into several SiHy macromer formulations. Experiments showed that comfort agents PNVP and Kollidon were the best candidates for such a procedure.

Over 60 proteins have been detected in the tear film and among these lysozyme has attracted the greatest attention. Several techniques for elucidating the identity, quantity and conformation of lysozyme deposited on soft contact lenses have been developed. Lysozyme also deposits on the newly introduced silicone hydrogel (SH) lens materials, but in extremely low levels compared to conventional hydrogel lenses. Hence, a major analytical complication with the study of the SH contact lens materials relates to the minute quantity of deposited lysozyme. The first project of this thesis involved the development of a method whereby lysozyme mass extracted from SH lens materials would be preserved over time and would be compatible with an optimized Western blotting procedure. This methodological development was incorporated into a clinical study (CLENS-100® and Silicone Hydrogels ? CLASH study) wherein the difference in the degree of total protein, the difference in lysozyme deposition and activity recovered from lotrafilcon A SH lens material when subjects used surfactant containing rewetting drops (CLENS-100®) versus control saline was investigated. The remaining experiments were in vitro experiments wherein the lenses were doped in artificial lysozyme solution containing ¹²⁵I-labeled lysozyme. These experiments were performed to gain insight into the kinetics of lysozyme deposition on SH lens materials and also the efficacy of a reagent in extracting lysozyme from SH lens materials. A protocol was developed whereby the percentage loss of lysozyme mass found on lotrafilcon A SH lenses was reduced from approximately 33% to <1% (p<0. 001), following extraction and resuspension. The results from the CLASH study demonstrated that when subjects used a surfactant containing rewetting drop instead of a control saline drop total protein deposition (1. 2±0. 7 µg/lens versus 1. 9±0. 8 µg/lens, p<0. 001), lysozyme deposition (0. 7±0. 5 µg/lens versus 1. 1±0. 7 µg/lens, p<0. 001) and percentage lysozyme denaturation (76±10% versus 85±7%, p=0. 002) were all reduced. The results from the kinetics study demonstrated that lysozyme accumulated rapidly on etafilcon A lenses (1 hr, 98±8 µg/lens), reached a maximum on the 7th day (1386±21 µg/lens) and then reached a plateau (p=NS). Lysozyme accumulation on FDA Group II and SH lenses continued to increase across all time periods, with no plateau being observed (p<0. 001). The results from the extraction efficiency study showed that 0. 2% trifluoroacetic acid/ acetonitrile was 98. 3±1. 1% and 91. 4±1. 4% efficient in extracting lysozyme deposited on etafilcon A and galyfilcon lenses, while the lysozyme extraction efficiency was 66. 3±5. 3 % and 56. 7±3. 8% for lotrafilcon A and balafilcon lens materials (p<0. 001). The results from these studies re-emphasize that novel SH lens materials are highly resistant to protein deposition and demonstrate high levels of biocompatibility.

The primary objective of this study was to quantify and characterise lipid deposition on soft (hydrogel) contact lenses, particularly those containing siloxane components. Studies involving a variety of in vitro doping and in vivo worn contact lenses were undertaken, in which lipid deposition was analyzed by either TLC or HPLC. Specific experiments were completed to optimize a method to extract the lipid from the lens materials, to compare the total lipid deposition on nine different hydrogel lenses and to analyze the effect that lipid deposition had on wettability. A method for extracting lipid from contact lenses using 2:1 chloroform: methanol was developed. This study also showed that siloxane-containing contact lens materials differ in the degree to which they deposit lipid, which is dependent upon their chemical composition. Small differences in lipid deposition that occur due to using variations in cleaning regimens were not identifiable through TLC, and required more sophisticated analysis using HPLC. Contact lens material wettability was found to be influenced by in vitro lipid deposition. Specifically, conventional hydrogels and plasma surface-treated silicone-hydrogel materials experienced enhanced wettability with lipid deposition. Reverse-phase HPLC techniques were able to quantify lipid deposits with increased sensitivity and accuracy. From the HPLC studies it was found that contact lens material, concentration of the lipid doping solution, and the composition of the lipid doping solution in in vitro deposition studies influenced the ultimate amount and composition of lipid deposits. In vivo HPLC studies showed that the final lipid deposition pattern was influenced by the interaction between the composition of the tear film and the various silicone hydrogel contact lens materials. In conclusion, HPLC analysis methods were more sensitive and quantitative than TLC. Lipid deposition was ultimately influenced by the concentration and composition of the lipid in the tear film and the contact lens material. Contact lens wettability was influenced by the presence and deposition of lipid onto the contact lens surfaces. Finally, this reverse-phase HPLC lipid analysis protocol was not the most sensitive, robust, or accurate. In the future, other methods of analysis should be explored.

Dry eye syndrome has been associated with the lack of phospholipids in the tear film, leading to disruption of the tear film and subsequent irritation. Characterization of the transport and release of phospholipids from a silicone hydrogel contact lens is required to assess the possible use of these lenses for phospholipid delivery to increase patient comfort. This thesis examines the use of silicone hydrogel contact lenses as phospholipid delivery devices. Contact lenses of silicone hydrogel composition were loaded with varying amounts of radiolabeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) from a solution of n-propanol. These lenses were eluted at 35°C into artificial tear fluid (ATF) or ATFcontaining varying amounts of DMPC. The amount of DMPC loaded into a lens is a linear function of the time of exposure to the DMPC/propanol solution. The initial rate of elution into ATF appears to be diffusion controlled for at least 10 hrs and is proportional to the amount of DMPC loaded. The ease of loading and the controllable release of DMPC from silicone hydrogels present the possibility of using such lenses to counter eye discomfort caused by inherently low levels of phospholipid in tears. To reduce manufacturing steps and concern for residual n-propanol in the lens, it is beneficial to incorporate the DMPC into the monomer formulation and then photopolymerize the lens. Results showed that using this process, DMPC can be placed in the lens and then eluted at faster rates than when it was loaded from n-propanol.

Purpose: To compare visual performance and acceptance of two different designs of monthly disposable silicone hydrogel multifocal contact lenses, the Air Optix Aqua Multifocal and the Biofinity Multifocal. Methods: A double masked randomised crossover trial of 62 presbyopic participants (between 41 and 60 years of age) was conducted. Participants were randomised first into either the Air Optix Aqua Multifocal or the Biofinity Multifocal lens to be worn for four weeks for each modality. There was a washout period of one week before wearing the second option. Measurements included binocular photopic distance visual acuity (VA), binocular photopic near VA, stereoacuity at distance and near and contrast sensitivity in photopic, mesopic and scotopic lighting conditions. Subjective participant experience for quality of vision was collected using the VF-14 visual function questionnaire and a specially designed daily diary. Results: Fifty-seven participants completed both periods of this crossover study (mean age 52.9, 43 females, 14 males). The difference for binocular photopic distance and near VAs between the Air Optix Aqua and Biofinity Multifocal were marginal (distance: p > 0.13, near: p > 0.24). Differences for stereoacuity at distance and near between the Air Optix Aqua and Biofinity Multifocal were not statistically significant (distance: p=0.33, near: p=0.36) and measurements for contrast sensitivity in mesopic and scotopic lighting conditions showed no statistically significant difference between the lens types (mesopic: p > 0.18 and scotopic: p > 0.31). Photopic contrast sensitivity showed statistically significant results and was marginally better with the Air Optix Aqua Multifocal than Biofinity Multifocal (p=0.013 by paired t-test and p=0.018 Wilcoxon Signed Ranks test). This was judged unlikely to be of clinical significance and most likely a chance finding. Marginal but not statistically significant preferences were found for the data of the VF-14 visual function questionnaire and the daily diary with participants preferring the Air Optix Aqua Multifocal for distance vision (distance vision scores: Wilcoxon Signed Ranks test: 79-76%) and reporting more satisfaction with intermediate and near vision with the Biofinity Multifocal lens design (intermediate vision scores: 66-60% and near vision scores: 74-72%). Comfort scores were equally high for both lens designs (comfort scores: 78- 82%). 43 participants (75%) felt soft multifocal contact lenses were a good alternative to spectacles and 33 participants (58%) were continuing to use one of the two designs one year after the trial ended. Of these, 17 wearers (51%) were wearing the Air Optix Aqua and 16 (49%) the Biofinity Multifocal lens. Conclusions: There were no consistent differences in visual performance between the Air Optix Aqua Multifocal and the Biofinity Multifocal lens design. The Air Optix Aqua multifocal was found to be marginally superior in participants’ subjective scores for binocular distance vision and the Biofinity Multifocal for binocular intermediate and near vision. Based on feedback at follow up, presbyopic participants in this research rated soft silicone hydrogel multifocal contact lenses a good alternative to spectacle wear.

The wettability of contact lenses has become an area of intense research, with the belief that the more "hydrophilic" or wettable the lens surface is, the more comfortable the lens may be, as the posterior surface of the eyelid will move more smoothly over it, hence increasing comfort.

There are many ways to assess the wettability of a given material, namely sessile drop,¹ captive bubble ² or Wilhelmy plate. ³ This thesis used the sessile drop method to determine the surface wettability of various hydrogel contact lens materials, by measuring the advancing contact angle made between the lens surface and a pre-determined volume of HPLC-grade water. This was followed by measuring the surface wettability following periods in which the lens materials were soaked in various contact lens care regimens. Further studies determined wettability of lens materials after various periods of in-eye wear and finally a study was undertaken to evaluate if a novel biological technique could be used to differentiate proteins that deposit on hydrogel lens materials that may affect wettability and cause discomfort.

A variety of hydrogel lenses, taken directly from their packaging and after soaking in various care regimens, were analyzed to determine their sessile drop advancing contact angles, in vitro. These studies indicated that poly-2-hydroxyethylmethacrylate (pHEMA)-based lenses are inherently more wettable than silicone-based lenses, unless they have a surface treatment that completely covers the hydrophobic siloxane groups. Additionally, certain combinations of lens materials and care regimens produce inherently more wettable surfaces when measured in vitro.

Suitable methods to assess contact lens wettability ex vivo, or after subjects had worn lenses for set periods of time, were developed. It was determined that using latex gloves to remove lenses had no impact upon the lens surface wettability and that rinsing of the lens surface after removal from the eye was required to determine the wettability of the underlying polymer.

The final wettability studies involved an analysis of various lens materials from clinical studies conducted within the Centre for Contact Lens Research (CCLR). These studies investigated differences in wettability between silicone hydrogel lenses manufactured from differing polymers and variations in ex vivo wettability of several combinations of lens materials and solutions, worn for varying periods of time.

A novel method to investigate proteins extracted from lenses using 2D-Difference in Gel Electrophoresis (DIGE) found that this technique could be used to analyze proteins extracted from contact lenses. The data obtained showed that there was no difference between a group of subjects who were symptomatic of lens-induced dryness or a control group, and that care solutions had a minimal influence on the pattern of deposition seen.

The overall conclusion of these studies is that hydrogel lens wettability is affected by the polymer composition and that care regimen components can modify the surface wettability.

This PhD project investigated the ramifications of air-cured and nitrogen-cured manufacturing processes during silicone hydrogel contact lens manufacture in terms of lens surface characterisation and clinical performance. A one-hour contralateral clinical study was conducted for ten subjects to compare the clinical performance of the two study lenses. The main clinical findings were reduced levels of subjective performance, reduced surface wettability and increased deposition. Contact angle analysis showed the air-cured lenses had consistently higher advancing and receding contact angle measurements, in comparison with the nitrogen-cured lens. Chemical analysis of the study lens surfaces in the dehydrated state, by x-ray photoelectron spectroscopy (XPS) and time-of-flight mass spectrometry (ToF-SIMS), showed no difference due to surface segregation of the silicone components. Analysis of frozen lenses limited surface segregation and showed a higher concentration of silicone polymer components and lower concentration of hydrophilic polymer components at the surface of the air-cured lens, in comparison with the nitrogen-cured lens. Scanning electron microscope (SEM) imaging showed the nitrogen-cured lens to have a surface typical of a hydrogel material, whereas the air-cured lens had regions of apparent phase separation. In addition, atomic force microscopy (AFM) showed the air-cured lens to have a rougher surface associated with greater adherence of contaminants (often observed in materials with reduced polymer cross-linking). In conclusion, clinical assessment of the study lenses confirmed the inferior performance of the air-cured lens. Surface analysis suggested that the non-wetting regions on the air-cured lenses were associated with elevated level of silicone components, reduced polymer cross-linking and polymer phase separation.

This thesis describes the impact of contact lens-related microbial keratitis in terms of incidence and severity. Disease outcome is defined by visual outcome, costs to the healthcare system, costs to the individual and duration of disease. A successful 12-month surveillance study was conducted of the populations of Australia and New Zealand to detect all cases of contact lens-related microbial keratitis. A random telephone survey of 32,000 households in Australia and 7,500 in New Zealand accurately determined the level of use of various contact lenses in the community. The impact of new contact lens types: silicone hydrogels and daily disposables were investigated. Increased risk persisted in overnight wear with silicone hydrogel materials. Microbial keratitis associated with silicone hydrogel materials had slightly shorter disease duration however other factors had a stronger influence on severity. Rigid gas permeable and frequent replacement soft lenses when used for daily wear constitute the lowest risk. Cost analysis was developed in a hospital case series of microbial keratitis. This analysis was applied in the surveillance study including cases managed in the private health care sector. Disease duration and associated costs are novel indices of severity for contact lens-related disease. The most dramatic effects on disease severity were seen with the type of organism involved. Keratitis attributed to environmental organisms (Gram-negative bacteria, Acanthamoeba, fungi and Nocardia species) were 10x more likely to cause loss of visual acuity, had longer duration of symptoms and incurred higher costs. Importantly, delays in receiving treatment increased disease duration and associated costs. Greater awareness of the need for specialist healthcare is indicated amongst health care providers and contact lens wearers. The hypothesis that overnight wear in silicone hydrogel lenses would not increase the risk of infection has been disproven. This information is of value to practitioners who are responsible for informing contact lens wearers about the risk of contact lens-related infections and should be weighed against the benefits of continuous wear. The identification of factors which contribute to the outcomes of disease will be used in education campaigns amongst health care providers and contact lens wearers to minimise the impact of disease.

This thesis investigates the feasibility of loading silicone hydrogel (SiHy) contact lenses with two different hydrophobic therapeutics, latanoprost and DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), for treatment of glaucoma and hyperemia respectively. The two methods of loading were 1) thermal loading in an aqueous medium and 2) convective loading in a solution of n-propanol. Dailies Total1® lenses prepared in this manner were tested for their loading and their release into artificial tears. Continuous release over 1-4 days at therapeutic levels is achievable from thermal loading of DMPC, convective loading of DMPC, and convective loading of latanoprost. The DMPC loading processes can be naturally integrated into standard manufacturing lines for Dailies Total1®. Both DMPC and latanoprost release at rates proportional to the amount loaded into a contact lens. Latanoprost loads into a contact lens strictly proportionally to the loading concentration and the time of loading. The convective loading step represents a significant improvement on both the time of loading (reduced from days to minutes) and the loading capacity of silicone hydrogel contact lenses. This thesis also compares the loading and release of latanoprost in the convective loading procedure using the SiHy contact lenses of Acuvue Advance® (Johnson & Johnson Vision Care, Jacksonville, FL) , Air Optix® (Alcon, Copenhagen, Denmark), Biofinity® (CooperVision), PureVision® (Bausch & Lomb), and Dailies Total1® (Alcon), and the polyHEMA lens, SofLens 38® (Bausch & Lomb), finding that silicone hydrogels load an order of magnitude more drug than the polyHEMA lens and release into artificial tears for an order of magnitude longer. Overall, these experiments provide a quantitative understanding of the dynamics of loading and release for both DMPC and latanoprost.

In this thesis, a comprehensive study of the electrical properties of carbon-hydrogen (CH) complexes in silicon (Si) and silicon-germanium (SiGe) alloys is presented. These complexes form by the reaction of residual carbon impurities with hydrogen that is introduced either by wet chemical etching or a dc hydrogen plasma. The complexes were detected and characterized by the deep level transient spectroscopy (DLTS), Laplace DLTS, and minority carrier transient spectroscopy (MCTS) technique. With this approach, properties like the activation enthalpy for carrier emission, the capture cross section, the charge state, and the thermal stability of the complexes were determined. The composition of the complexes was derived from the analysis of their depth profiles in samples with different impurity concentrations. Using these methods, eight carbon-hydrogen related defect levels (E42, E65, E75, E90, E90', E262, H50, H180) and one hydrogen related level (E150) were detected in Si, SiGe alloys and Ge. Hydrogen plasma treatment at temperatures around 373 K introduces four dominant traps in Si at about Ec-0.06 eV (E42), Ec-0.52 eV (E262), Ev+0.33 eV (H180), and Ev+0.08 eV (H50). E42 and E262 are shown to be two charge states of the same defect. The characteristic field dependence of their emission rate links E42 with the double acceptor level and E262 with the single acceptor level of a CH complex. By comparison of their properties with calculations they are assigned to the anti-bonding configuration of the CH complex (CH_1AB). H180 was previously suggested to be the donor state of the CH_1AB configuration. This hypothesis could not be confirmed. Instead, it is shown that H180 exhibits a barrier for hole capture of about 53 meV, which hinders the reliable determination of its charge state from the field dependence of the emission rate. However, its activation enthalpy is in reasonable agreement with the predicted level position of the acceptor state of the CH_T configuration of CH, where H sits on the tetrahedral interstitial (T) position next to carbon. Therefore, H180 is tentatively assigned to CH_T. H50 is reported for the first time and it appears with concentrations close to the detection limit of the DLTS technique (~1E11 cm^-3). This complicates the determination of its charge state. Nevertheless, theory predicts the acceptor level of the CH_2AB configuration at about Ev+0.07 eV, which is remarkably close to the experimental value of H50. Therefore, H50 is tentatively assigned to the acceptor level of CH_2AB. In contrast, hydrogenation of silicon by wet chemical etching introduces three dominant levels at Ec-0.11 eV (E65), Ec-0.13 eV (E75), and Ec-0.16 eV (E90). Previously, E90 was contradictorily assigned by different authors to the donor and to the acceptor state of the bond-centered configuration of the CH complex (CH_1BC). In this work, this contradiction is resolved. It is shown that two different defect levels (E90 and E90') appear in the DLTS spectra at about 90 K in samples with a low oxygen concentration (< 1E17 cm^-3). The acceptor state of the CH_1BC configuration (E90) can be observed directly after hydrogenation by wet chemical etching or a dc hydrogen plasma treatment at temperatures below 373 K. In contrast, the donor state of a CH_n complex (E90', Ec-0.14 eV), that involves more than one hydrogen atom, is formed by a reverse bias annealing of samples with a net donor concentration of Nd > 1E15 cm^-3. By comparison with theory it is concluded that n > 2. In samples with a high oxygen concentration (> 1E17 cm^-3) E65 and E75 are dominant. Both levels belong to the CH_1BC configuration disturbed by a nearby oxygen atom. The appearance of two levels is the result of two inequivalent positions of the oxygen atom in respect to the CH bond. E42, E90, E262, and H180 are also investigated in diluted SiGe alloys to analyze the influence of alloying on their electrical properties. The presence of Ge atoms in the closest environment of the defects leads to the appearance of additional defect levels close to those observed in pure Si. The relative concentration of these additional defects is in agreement with models of the proposed defect structure of E42, E90, E262, and H180. An increase of the Ge content in SiGe alloys leads to a shift of the defect levels in the band gap of SiGe. An extrapolation of this shift predicts the appearance of E90 and E262 also in pure Ge. A hydrogen related level E150 (Ec-0.31 eV) is indeed observed in hydrogenated n-type Ge. Its concentration is significantly higher after hydrogen plasma treatment than after wet chemical etching. It is shown that E150 contains a single hydrogen atom and involves an unknown impurity, most likely carbon, oxygen, or silicon. E150 represents a reasonable candidate for a CH complex in Ge
In dieser Arbeit werden die elektrischen Eigenschaften von Kohlenstoff-Wasserstoff-Komplexen in Silizium (Si) und Silizium-Germanium-Legierungen (SiGe) studiert. Diese Komplexe bilden sich durch Reaktion von Kohlenstoff-Verunreinigungen mit Wasserstoff, welcher durch nasschemisches Ätzen oder eine Wasserstoffplasma-Behandlung eingebracht wird. Der Nachweis und die Charakterisierung der Defekte erfolgte mit den Methoden der Kapazitätstransientenspektroskopie (DLTS), Laplace DLTS und der Minoritätsladungsträgertransientenspektroskopie (MCTS). Damit wurden Eigenschaften wie die Aktivierungsenergie der Ladungsträgeremission, die Einfangquerschnitte, der Ladungszustand und die thermische Stabilität der Komplexe bestimmt. Die Zusammensetzung der Komplexe wurde durch eine Analyse der Tiefenprofile ermittelt, welche in Proben mit verschiedenen Verunreinigungskonzentrationen gemessen wurden. Mit diesen Methoden wurde acht Kohlenstoff-Wasserstoff-korrelierte Defektniveaus (E42, E65, E75, E90', E90, E262, H50, H180) in Si und SiGe und ein Wasserstoff-korreliertes Niveau in Ge nachgewiesen. Eine Wasserstoffplasma-Behandlung bei Temperaturen um 373 K erzeugt vier dominante Defektniveaus in Si bei Ec-0.06 eV (E42), Ec-0.52 eV (E262), Ev+0.33 eV (H180) und Ev+0.08 eV. Es wird gezeigt, dass E42 und E262 zwei Ladungszustände desselben Defektes sind. Die charakteristische Feldabhängigkeit der Emissionsrate zeigt, dass E42 der Doppel-Akzeptor- und E262 der Einfach-Akzeptor-Zustand eines CH-Komplexes ist. Durch Vergleich der beobachteten Eigenschaften mit theoretischen Berechnungen werden beide Niveaus der antibindenden Konfiguration des CH-Komplexes (CH_1AB) zugeordnet. Das Niveau H180 wurde in der Literatur bisher mit dem Donator-Zustand der CH_1AB-Konfiguration in Verbindung gebracht. Diese Hypothese konnte nicht bestätigt werden. Es wird gezeigt, dass H180 eine Barriere für den Löchereinfang von etwa 53 meV besitzt, was die Bestimmung des Ladungszustandes aus der Feldabhängigkeit der Emissionsrate erschwert. Die Aktivierungsenergie von H180 stimmt jedoch befriedigend mit der berechneten Aktivierungsenergie des Akzeptorzustandes der CH_T-Konfiguration überein, bei der H auf der T-Zwischengitterposition sitzt. Daher wird H180 vorläufig dem CH_T-Komplex zugeordnet. Das Niveau H50, welches zum ersten Mal hier beschrieben wird, wird nur mit sehr geringen Konzentrationen nachgewiesen. Dies erschwert die Bestimmung des Ladungszustandes. Die Aktivierungsenergie von H50 stimmt jedoch auffallend gut mit dem von der Theorie vorhergesagten Akzeptorniveau von CH_2AB (Ev+0.07 eV) überein. Daher wird H50 vorrübergehend CH_2AB zugeordnet. Das Einbringen von Wasserstoff in Silizium durch nasschemisches Ätzen führt zu drei dominanten Defektniveaus bei Ec-0.11 eV (E65), Ec-0.13 eV (E75) und Ec-0.16 eV (E90). E90 wurde bisher widersprüchlich von verschiedenen Autoren dem Donatorzustand und dem Akzeptorzustand der bindungszentrierten Konfiguration (CH_1BC) des CH-Komplexes zugeordnet. Dieser Widerspruch konnte aufgelöst werden. Es wird gezeigt, dass in Silizium mit niedrigem Sauerstoffanteil (< 1E17 cm^-3) zwei verschiedene Defektniveaus (E90 und E90') bei etwa 90 K in den DLTS-Spektren erscheinen, welche nur mit der Laplace DLTS-Technik aufgelöst werden können. Der Akzeptorzustand der CH_1BC-Konfiguration kann direkt nach nasschemischem Ätzen oder einer Wasserstoffplasma-Behandlung bei 373 K beobachtet werden. Im Gegensatz dazu wird durch eine Sperrspannungs-Temperung in Proben mit einer Donatorkonzentration von Nd > 1E15 cm^-3 der Donatorzustand eines CH_n-Komplexes (E90', Ec-0.14 eV), welcher mehr als ein Wasserstoffatom enthält, gebildet. Durch Vergleich mit theoretischen Berechnungen wird n > 2 geschlussfolgert. Die Niveaus E65 und E75 sind in Proben mit einem hohen Sauerstoffanteil (> 1E17 cm^-3) dominant. Beide Niveaus gehören zu einer durch ein O-Atom verzerrten CH_1BC-Konfiguration. Das Auftreten von zwei Niveaus wird durch zwei nicht-äquivalente Positionen des O-Atoms bezüglich der CH-Bindung erklärt. Die Eigenschaften von E42, E90, E262 und H180 wurden ebenfalls in verdünnten SiGe-Legierungen untersucht. Es wird gezeigt, dass Ge-Atome in der direkten Umgebung der Defekte zusätzliche Defektniveaus erzeugen, die in der Bandlücke nahe zu den Si-Defektniveaus liegen und von durch Ge-Atomen verzerrten Defekten stammen. Die beobachteten relativen Konzentrationen dieser Ge-korrelierten Niveaus kann mit Modellen der atomaren Struktur der Defekte erklärt werden. Eine Verschiebung der Defektniveaus proportional zum Ge-Anteil in der Legierung wurde beobachtet. Eine Extrapolation dieser Verschiebung legt den Schluss nahe, dass E90 und E262 auch in reinem Ge beobachtbar sein sollten. Tatsächlich wurde ein Wasserstoff-korrelierter Defekt E150 (Ec-0.31 eV) in n-Typ Germanium beobachtet. Die Konzentration von E150 ist nach einer Wasserstoffplasma-Behandlung wesentlich höher als nach nasschemischen Ätzen. Es wird gezeigt, dass E150 ein einzelnes Wasserstoffatom und ein noch unbekanntes Verunreinigungsatom enthält, höchstwahrscheinlich Kohlenstoff, Sauerstoff oder Silizium. Damit ist E150 ein sehr wahrscheinlicher Kandidat für einen CH-Komplex in Germanium

This dissertation focuses on the characterization of hydrogen implanted 3C-SiC and helium implanted 6H-SiC and the interaction of silver and palladium with the SiC. The main technique used for the analysis of the implanted SiC was transmission electron microscopy (TEM), although scanning electron microscopy (SEM) and nanoindentation hardness testing were also used. Both H and He implantations were done at an ion energy of 100 keV and the total dose for both species was 1017 ions/cm2. Specimens were annealed at 1000 °C for 20 min in an inert atmosphere. The observed depth of ion damage agreed closely with that predicted by TRIM 2008. The damaged region in the He implanted specimens had a high density of small bubbles but no cracks were observed. Severe cracking was observed along the damaged region in the H implanted specimens. A second phase hexagonal (4H-SiC) was detected in two grains in the 3C-SiC and some grown in voids were also observed. The wettability of SiC by a 2:1 by volume mixture of Ag and Pd is extremely low but is significantly increased through the addition of Si to the mixture. The Si containing metal mixture was found to migrate along the grain boundaries of polycrystalline 3CSiC while sealing the point of entry. Pd attacks SiC and severe etching was observed on the surface of 6H-SiC. An epitaxially orientated Pd2Si inclusion was observed in the 6H-SiC. No effect of implantation damage on the interaction of Pd and Ag with SiC was observed. Pd etched the surface of the He implanted 6H-SiC down through the damaged region with no evidence of implantation damage left after 67 hours of annealing and thus no conclusions could be drawn. The metal mixture interacted with the non implanted surface of the H implanted 3C-SiC after dissolving the Si substrate and therefore the effect of the ion damage on the interaction could not be investigated. Nanoindentation hardness measurements showed a marked increase in hardness of He implanted 6H-SiC annealed for 20 min at 1000 °C over that of as implanted and virgin material. There was also a large decrease in hardness corresponding to the depth of the ion damage.

Secondary ion mass spectrometry (SIMS) has been employed tostudy the spatial distributions resulting from mass transportby diffusion and ion implantation in single crystal siliconcarbide (SiC). By a systematic analysis of this data,fundamental processes that govern these phenomena have beenderived.

The acceptor atoms Al and B are known to be electricallypassivated by H in SiC. By studying the thermally stimulatedredistribution of implanted deuterium (2H) in various acceptordoped structures, it is found that hydrogen forms complexeswith the doping atoms, and also interacts strongly withimplantation induced defects. A comprehensive understanding ofthe formation and dissociation kinetics of these complexes hasbeen obtained. The extracted effective capture radius for theformation of 2H-B complexes is in good agreement with thatexpected for a coulomb force assisted trapping mechanism. Thelarge difference of 0.9 eV in the extracted dissociationenergies for the 2H-Al and 2H-B complexes suggests that theatomic configurations of the two complexes are significantlydifferent. Furthermore, by studying the migration behavior of Hin the presence of built-in electric fields, it is concludedthat all of the mobile H is in the positive charge state inp-type SiC.

A large number of implantations have been performed withrespect to ion mass, energy, fluence, and crystal orientation.The electronic stopping cross sections in the low velocityregime for ions with atomic numbers 1 ≤ Z1 ≤ 15have been extracted from the ion range distributions. Theydisplay both Z1-oscillations and a smaller than velocityproportional stopping for ions with Z1 ≤ 8, in agreementwith previous reports for other materials. Furthermore, thedegree of ion channeling in various major axial and planarchannels of the 6H and 4H-SiC crystal has been explored. Twotypes of ion implantation simulators have been developed. Onebased on a statistical, data-base approach, and one atomisticsimulator, based on the binary collision approximation (BCA).By fitting BCA simulated profiles to the experimental profiles,detailed information about the electronic stopping andimplantation induced damage is extracted. In addition, thevacancy-related damage caused by the implantations has beeninvestigated by positron annihilation spectroscopy (PAS). Twotypes of implantation induced positron traps have been isolatedand are tentatively identified as a Si vacancy (VSi) and a Si-Cdivacancy (VSiVC). The extension of detected VSi is in goodagreement with that predicted by BCA simulations, and forimplantations with heavier ions VSi are revealed at far greaterdepths than the mean projected ion range due to deeplypenetrating channeled ions.

Quantum computers have been the dream of many scientists for over thirty years but the fact such devices still consist of only a handful of quantum bits (qubits) highlights the fact that this is not a trivial concept. However the potential of powerful parallelisation, which could out perform classical computers remains a huge incentive for researchers. Interest in donors in silicon has grown since being put forward as a possible candidate for a qubit in 1998 by Kane. Group V atoms, such as phosphorus, substitute into the silicon lattice but possess an extra outer shell electron compared to the neighbouring silicon atoms. This electron orbits the donor much like a hydrogen atom trapped in a silicon crystal. Despite overlapping with thousands of silicon atom, the donor electron experiences very little interaction with its surroundings leading to long spin lifetimes and coherence times. In this thesis the orbital state of donor electrons is explored. Electrical detection is used as a method of reading out coherent and incoherent manipulations of donor orbits. This is due to the high sensitivity achievable with electrical measurements. This work looked the detection mechanism in low and high intensity regimes as well as exploring the dynamics of the electron donor system in the time domain. Such experiments are use to measure the saturation of absorption and the electron-ion recombination rate (a quantity for which a range of values have previously been reported). Finally, the first electrical detection of coherent control of orbital states in silicon donors is presented, with T.J. found to be 30 - SOps.

En France, les matériaux à base de ciment sont utilisés comme matrice de conditionnement des déchets nucléaires de faible et moyenne activité. La radiolyse de l'eau est due aux déchets nucléaires stockés dans les matériaux. La formation de ses produits radiolytiques tels que le gaz H₂ doit être évaluée pour des raisons de sécurité. Les silicates de calcium hydratés (C-S-H) représentent le principal produit (50%) d'hydratation du ciment Portland (CP). L’objectif de cette étude est de comprendre les mécanismes radiolytiques de la production d'hydrogène dans les C-S-H, d'étudier l'effet d'impuretés (telles que des ions alcalins, hydroxydes ou nitrates supplémentaires) sur la production de gaz H₂ dans les C-S-H et d'examiner l'existence d'interactions entre les phases principales (C-S-H et portlandite) du ciment Portland. Après avoir caractérisé les échantillons par diverses techniques, ils ont été soumis à différents types d'irradiation (faisceaux gamma et électrons et ions lourds (HI) pour déterminer leur rendement radiolytique en H₂, G(H₂). Dans les C-S-H, il a été démontré que, sous irradiation gamma, la production d’H₂ est indépendante de la teneur en eau et que les C-S-H produisaient autant d’H₂ que la même masse d’eau. Ainsi, le mécanisme de production d’hydrogène est très efficace dans les C-S-H. La comparaison entre les résultats obtenus sous rayons gamma et ceux obtenus sous HI implique qu’il n'y a pas ou peu d'effet de transfert d’énergie linéique (TEL) dans les C-S-H. Ainsi, les réactions de recombinaison semblent limitées. L’introduction d’ions nitrates dans la structure des C-S-H induit une diminution importante du G(H₂). L’irradiation des hydrates de C2S et C3S constitués majoritairement de C-S-H et de portlandite indique qu’il n’y a pas de phénomènes de transfert d’énergie entre ces phases. Enfin, les expériences de spectroscopie par résonance paramagnétique électronique (RPE) ont permis de proposer des mécanismes radiolytiques dans les C-S-H. L’ensemble de ces résultats nous permettent de mieux comprendre les effets d’irradiation dans les ciments
In France, cementitious materials are used as conditioning matrix of low level and intermediate level nuclear wastes. Water radiolysis occurs due to the nuclear wastes stored in the materials. The formation of its radiolytic products such as H₂ gas must be evaluated for safety reasons. Calcium silicate hydrate (C-S-H) is the main product (50%) of hydration of Portland Cement (PC). The aim of this study is to understand the radiolytic mechanisms of the hydrogen production in C-S-H, to investigate the effect of impurities (such as alkali ions, additional hydroxides or nitrates ions) on H₂ gas production in C-S-H and to examine if interactions exist between different main phases (C-S-H and portlandite) in cement matrix. After using various characterization techniques, samples were submitted to different types of irradiation (gamma rays and electrons and heavy ions (HI) beams) to determine their H₂ radiolytic yield, G(H₂). In C-S-H system, it has been shown, under gamma irradiation, that G(H₂) does not depend on water content, moreover, C-S-H system itself produce efficiently H₂ gas. The comparison between the results obtained under gamma rays and that obtained under HI implies: there is no/ low LET effect in C-S-H. While with nitrate ions in C-S-H, a large decrease of G(H₂) is observed. Irradiation of C2S and C3S hydrates mainly composed of C-S-H and portlandite shows that here is no energy transfer phenomena between these two phases. Finally, the electron paramagnetic resonance (EPR) spectroscopy experiments have enabled proposing radiolytic mechanisms. All these results help us to understand the radiation effects in cements

A mass manufacturable impedance based, palladium doped porous silicon sensor, was fabricated for hydrogen detection. The sensor was built using electrochemical etching to produce mesoporous silicon. Four nanometers of palladium was defused directly into the porous silicon and another four nanometers of Pd was deposited on the defused surface to enhance sensing. The sensor was tested in a sealed chamber in which the impedance was measured while hydrogen in nitrogen was ranged from 0-2 percent. Unlike conventional hydrogen sensors this sensor responded at room temperature to changes in hydrogen concentration. The electrical impedance response due to adsorption and desorption of hydrogen reacted relatively quickly due to the nanoparticle nature of palladium diffusion in and Pd evaporation on porous silicon.

Le sujet de cette thèse est lié à l'étape d'implantation de la technologie Smart Cut™. Cette technologie utilise l'hydrogène pour transférer des couches de silicium sur des substrats isolants. Le transfert se fait par une fracture induite par la formation des défauts bidimensionnels appelés dans la littérature des plaquettes (en anglais « platelets »). Plus précisément, nous avons étudié dans le cadre de cette thèse les défauts qui apparaissent dans l'état post implantation et leur évolution de l'endommagement d'implantation vers l'état qui contient des plaquettes. L'étude est organisée en deux parties : une première partie qui contient les résultats obtenus par simulation atomistique et une deuxième partie qui contient l'étude par spectroscopie infrarouge de l'évolution des concentrations des défauts suites à des recuits à différentes températures. Les simulations atomistiques ont été effectuées dans le cadre de la théorie de la fonctionnelle densité et ont permis de calculer des énergies de formation et de migration/recombinaisons. Les défauts étudiés sont les interstitiels d'hydrogène atomique et moléculaire, des lacunes et multi-lacunes hydrogénées et finalement des différents modèles de plaquettes. Ces énergies ont permis réaliser un schéma hiérarchique de stabilité des défauts. Ce schéma a été confronté avec des analyses infrarouge sur des échantillons de silicium implanté par hydrogène (à 37 keV) dans le régime dit de «sous-dose» qui ne permets habituellement la formation immédiate des plaquettes lors de l'étape de l'implantation. Ces analyses ont permis de discriminer des évolutions des concentrations de défauts déduites des comportements lors des recuits des pics correspondants aux défauts. La comparaison entre ces évolutions et le schéma énergétique a permis de valider un scénario d'évolution des défauts vers l'état plaquette
The topic of this thesis is related to the implantation step of the Smart Cut™ technology. This technology uses hydrogen in order to transfer silicon layers on insulating substrates. The transfer is performed through a fracture induced by the formation of bidimensional defects well known in Iiterature as "platelets". More exactly, we have studied within this thesis work the defects appearing in the post implant state and the evolution of the implantation damage towards a state dominated by platelets. The study is organised into two parts: in the first part we present the results obtained by atomic scale simulations while the second part we present an infrared spectroscopy study of the evolution of defects concentrations after annealing at different temperatures. The atomic scale simulations have been performed within the density functional theory and they allowed us to compute the formation energies and the migration and recombination barriers. The defects included in our study are: the atomic and diatomic interstitials, the hydrogenated vacancies and multivacancies and the several platelets models. The obtained energies allowed us to build a stability hierarchy for these types of defects. This scheme has been confronted with some infrared analysis on hydrogen implanted silicon samples (37 keV) in a sub-dose regime which does not allow usually the formation of platelets during the implantation step. The analysis of the infrared data allowed the detailed description of the defects concentration based on the behaviour of peaks corresponding to the respective defects during annealing. The comparison between these evolutions and the energy scheme obtained previously allowed the validation of an evolution scenario of defects towards the platelet state

This thesis examines the optical properties of nanoscale silicon and the sensitization of Er with Si. In this context, it predominantly investigates the role of defects in limiting the luminescence of Si nanocrystals, and the removal of these defects by hydrogen passivation. The kinetics of the defect passivation process, for both molecular and atomic hydrogen, are studied in detail. Moreover, the optical absorption of Si nanocrystals and the effect of annealing environment (during nanocrystal synthesis) on the luminescence are investigated. The effect of annealing temperature and hydrogen passivation on the coupling (energy transfer) of Si nanocrystals to optically active centres (Er) is also examined.¶ The electronic structure of silicon-implanted silica slides is investigated through optical absorption measurements. Before and after annealing to form Si nanocrystals, optical absorption spectra from these samples show considerable structure that is characteristic of the particular implant fluence. This structure is shown to correlate with the transmittance of the samples as calculated from the modified refractive index profile for each implant. Due to the high absorption coefficient of Si at short wavelengths, extinction at these wavelengths is found to be dominated by absorption. As such, scattering losses are surprisingly insignificant. To eliminate interference effects, photothermal deflection spectroscopy is used to obtain data on the band structure of Si in these samples. This data shows little variance from bulk Si structure and thus little effect of quantum confinement. This is attributed to the dominance of large nanocrystals in the absorption measurements.¶ The effect of annealing environment on the photoluminescence (PL) from silicon nanocrystals synthesized in fused silica by ion implantation and thermal annealing is studied as a function of annealing temperature and time. Interestingly, the choice of annealing environment (Ar, N2, or 5 % H2 in N2) is found to affect the shape and intensity of luminescence emission spectra, an effect that is attributed both to variations in nanocrystal size and the density of defect states at the nanocrystal/oxide interface.¶ The passivation kinetics of luminescence-quenching defects, associated with Si nanocrystals in SiO2, during isothermal and isochronal annealing in molecular hydrogen are studied by time-resolved PL. The passivation of these defects is modeled using the Generalized Simple Thermal model of simultaneous passivation and desorption, proposed by Stesmans. Values for the reaction-rate parameters are determined for the first time and found to be in excellent agreement with values previously determined for paramagnetic Si dangling-bond defects (Pb type centers) found at planar Si/SiO2 interfaces; supporting the view that non-radiative recombination in Si nanocrystals is dominated by such defects.¶ The passivation kinetics of luminescence-quenching defects during isothermal and isochronal annealing in atomic hydrogen are studied by continuous and time-resolved PL. The kinetics are compared to those for standard passivation in molecular hydrogen and found to be significantly different. Atomic hydrogen is generated using the alneal process, through reactions between a deposited Al layer and H2O or –OH radicals in the SiO2. The passivation and desorption kinetics are shown to be consistent with the existence of two classes of nonradiative defects: one that reacts with both atomic and molecular hydrogen, and the other that reacts only with atomic hydrogen. A model incorporating a Gaussian spread in activation energies is presented that adequately describes the kinetics of atomic hydrogen passivation and dissociation for the samples.¶ The effect of annealing temperature and hydrogen passivation on the excitation cross-section and PL of erbium in silicon-rich silica is studied. Samples are prepared by co-implantation of Si and Er into SiO2 followed by a single thermal anneal at temperatures ranging from 800 to 1100 degrees C, and with or without hydrogen passivation performed at 500 degrees C. Using time-resolved PL, the effective erbium excitation cross-section is shown to increase by a factor of 3, while the number of optically active erbium ions decreases by a factor of 4 with increasing annealing temperature. Hydrogen passivation is shown to increase the luminescence intensity and to shorten the luminescence lifetime at 1.54 micron only in the presence of Si nanocrystals. The implications of these results for realizing a silicon-based optical amplifier are also discussed.

The electronic structure factors that control Si-H and Ge-H bond activation by transition metals are investigated by means of photoelectron spectroscopy. Molecular orbital calculations are also used to gain additional insight into the orbital interactions involved in bond activation. The complexes studied have the general molecular formula (η⁵-C₅R'₅)Mn(CO)(L)HER₃, where R' is H or CH₃, L is CO or PMe₃, E is Si or Ge and R is Ph or Cl. These compounds are interesting models for catalysts in industrial processes like hydrosilation. The compounds display different stages of interaction and "activation" of the E-H bonds with the metal. One purpose is to measure the degree of Mn, Si, H 3-center-2-electron bonding in these complexes. The three-center interaction can be tuned by changing the substituents on Si, methylating the cyclopentadienyl ring, changing the ligand environment around the metal and substituting Si with Ge. The degree of activation is measured by observing the shifts in the metal and ligand ionizations relative to starting materials and free ligand in the photoelectron spectrum. Changing the substituent on Si extensively changes the degree of activation. Photoelectron spectral studies on (η⁵-C₅H₅)Mn(CO)₂HSiPh₃ show this to be a Mn(I) system. Progressive methylation of the cyclopentadienyl ring increases the electron richness at the metal center with no substantial effect on the degree of activation. Substitution on the metal (PMe₃ for CO) is less able to control the electronic structure factors of activation than the substitution on the Si atom. The magnitude of Ge-H bond activation is found to be of the same order as the Si-H bond activation for analogous compounds as found by studying (η⁵-C₅H₅)Mn(CO)₂HGePh₃, (η⁵-CH₃C₅H₄)Mn(CO)₂HGePh₃ and (η⁵- C₅(CH₃)₅)Mn(CO)₂HGePh₃ complexes by photoelectron spectroscopy. The photoelectron spectra of CpFe(CO)₂SiCl₃ and CpFe(CO)₂SiMe₃ were measured to study the electron charge shift from the metal to the ligand in these complexes as compared to CpMn(CO)₂HSiR₃ complexes. The photoelectron spectroscopic studies include numerous perturbations of the ligand and metal center to observe the extent of bond interaction and remain one of the best techniques to detect activation products.

The unique compressive, optical, and biocompatible properties of silicone hydrogels allow them to be used in a wide variety of applications in the biomedical field. However, the relatively weak mechanical behavior, as well as the highly deformable nature of these elastomeric materials, presents a myriad of challenges when attempting to understand their constitutive and fracture properties in order to improve hydrogel manufacturing and performance in applications. In this thesis, a series of experimental techniques were developed or adapted from common engineering approaches in order to investigate the effects of rate and temperature on the viscoelastic constitutive and fracture behavior of two solvated semi-interpenetrating polymer network silicone hydrogel systems. Viscoelastic characterization of these material systems was performed by implementing a series of uniaxial tension and dynamic mechanical analysis shear tests in order to generate relevant master curves and corresponding thermal shift factors of such properties as shear relaxation modulus, dynamic moduli, and the loss factor. Concurrently, the cohesive fracture properties were studied by utilizing a â semi-infiniteâ strip geometry under constrained tension in which thin pre-cracked sheets of these cured hydrogels were exposed to several different loading conditions. Fracture tests were performed over a relevant range of temperatures and crosshead rates to determine and generate a master curve of the subcritical strain energy release rate. Experimental methods utilizing high-speed camera images and digital image correlation to monitor viscoelastic strain recovery in the wake of a propagating crack were explored. The results from this thesis may prove useful in an investigation of the interfacial fracture of these hydrogel systems on several different polymer substrates associated with an industrial manufacturing problem.
Master of Science

Photovoltaics offers a unique solution to energy and environmental problems simultaneously. However, widespread application of photovoltaics will not be realized until costs are reduced by about a factor of four without sacrificing performance. Silicon crystallization and wafering account for about 55% of the photovoltaic module manufacturing cost, but can be reduced significantly if a ribbon silicon material, such as String Ribbon Si, is used as an alternative to cast Si. However, the growth of String Ribbon leads to a high density of electrically active bulk defects that limit the minority carrier lifetime and solar cell performance. The research tasks of this thesis focus on the understanding, development, and implementation of defect passivation techniques to increase the bulk carrier lifetime in String Ribbon Si in order to enhance solar cell efficiency. Hydrogen passivation of defects in Si can be performed during solar cell processing by utilizing the hydrogen available during plasma-enhanced chemical vapor deposition (PECVD) of SiNx:H films. It is shown in this thesis that hydrogen passivation of defects during the simultaneous anneal of a screen-printed Al layer on the back and a PECVD SiNx:H film increases the bulk lifetime in String Ribbon by more than 30 ?A three step physical model is proposed to explain the hydrogen defect passivation. Appropriate implementation of the Al-enhanced defect passivation treatment leads to String Ribbon solar cell efficiencies as high as 14.7%. Further enhancement of bulk lifetime up to 92 ?s achieved through in-situ NH3 plasma pretreatment and low-frequency (LF) plasma excitation during SiNx:H deposition followed by a rapid thermal anneal (RTA). Development of an optimized two-step RTA firing cycle for hydrogen passivation, the formation of an Al-doped back surface field, and screen-printed contact firing results in solar cell efficiencies as high as 15.6%. In the final task of this thesis, a rapid thermal treatment performed in a conveyer belt furnace is developed to achieve a peak efficiency of 15.9% with a bulk lifetime of 140 ?Simulations of further solar cell efficiency enhancement up to 17-18% are presented to provide guidance for future research.

碩士
國立聯合大學
化學工程學系碩士班
106
In our study, a sol-gel process was used to synthesize the organic-inorganic hybrid prepolymers. The prepolymers were mixed with other formulas by photo-polymerization method to obtain the high oxygen permeability and functional silicone hydrogels for the applications of soft contact lens. In addition, the effect of prepolymer’s content on the properties of the silicone hydrogels was carried out by various analysis methods. The ratio of prepolymers affects the hydrophilicity/ hydrophobicity and degree of cross-linking of hydrogels, but also influence the swelling behavior, contact angle, mechanical properties and the thermal behavior states of water of the silicone hydrogels. The results show that the hydrogels follow the Non-Fickian diffusion (Case III) model via the swelling kinetics analysis, and the mechanism exponent (n) range of the samples was from 0.5 to 1, meaning that the relaxation rate of the polymer chain was similar to the solvent diffusion rate. According to ISO10993-5 method by the vitro cytotoxicity test, the functional silicone hydrogels expressed no toxic response and has good biocompatibility. Apart from that, the formulation of hydrogels incorporated the natural health-care pigment, which expressed a good light filtering ability and prevented eye damage in the short-wavelength blue light range (381-460nm). And the blue light blocking function of natural pigment was not only better than that of commercial products, but also has the function of alleviating eye fatigue. In the eye care drug (Vitamin B12) loading release experiment, n value was about 0.5, which was close to the ideal Fick's diffusion mechanism. It illustrated that the silica hydrogels could adjust the diffusion rate by the drug concentration.

碩士
國立臺灣科技大學
材料科學與工程系
105
This study is to synthesize positively charged silicon hydrogel, so that the moisturizing agent in the preserving buffer solution can be attacted to positively charged silicon hydrogel to improve the surface wettability of contact lens. The main component of this hydrogel is hydroxyl-terminated polydimethyl siloxane (PDMS-diol), which serves as the soft segment of a polyurethane (PU) macromer. After reacting with isophorone diisocyanate (IPDI), polyethylene glycol 600 (PEG 600) was added to increase the hydrophilicity of the resultant PU. Then 2-(dimethylamino)ethyl methacrylate (DMAEMA) was attached to the ends of the PU to provide the ionic moiety. Finally, a second network was polymerized from N,N-dimethylacrylamide (DMA) through UV initiation. FTIR analysis was performed to verify the chemical structure. The surface ionic functional groups of the film was determined using dyeing test. Further characterization of the resultant hydrogel included the equilibrium water content (EWC), oxygen permeability (Dk), SEM-EDS, contact angle, tensile tests, protein deposition, and cytotoxicity against L-929 fibroblasts. From the results, this silicone-containing hydrogel can be used for short-term biomedical applications.

碩士
國立聯合大學
化學工程學系碩士班
103
Oxygen permeability (Dk) and transmissibility (Dk/t) are important parameters used to assess the suitability of contact lenses. The oxygen permeability of the material describes its intrinsic ability to transport oxygen. In this study, we design a novel apparatus to measure Dk and Dk /t of contact lenses by the titration. The apparatus involves accurate measurement of oxygen across the material by allowing the gas (oxygen) to pass through a specially fabricated steel lens model. The expelled gas was collected by dissolution in DI water and the oxygen was measured by titration of the solvent. The Dk and Dk/t values were carried out by this method compared with the oxygen permeability standard values of commercially available contact lenses. The results showed that the method is simple, cost down, requiring no sophisticated equipment as well as giving accurate values in a short time. In addition, there were two types of silicone hydrogel lens materials, HEMA / TEOS and HEMA / TRIS / TEOS, were prepared by the sol-gel process and light polymerization method with suitable components and synthetic conditions. In the HEMA / TEOS recipe, adding 5% of Tetraethyl orthosilicate (TEOS), the Dk and Dk / t values of silicone hydrogel lens are 91 and 75, respectively. The result not only can improve the oxygen permeability effectively, but also is better than that of commercial silicone hydrogel (Dk and Dk / t values were 85 and 45). In the HEMA / TRIS / TEOS recipe, adding 5% of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate(TRIS) into the main recipe 2-Hydroxyethyl methacrylate (HEMA), the Dk and Dk / t values were 114 and 74. These data are similar to the HEMA / TEOS recipe. However, then adding 5% of TEOS into HEMA / TRIS system, which show an excellent oxygen permeability, the Dk and Dk / t values are 136 and 114. This result has been far higher than that of the commercially available products, this recipe for improving the oxygen permeability of the silicone hydrogel contact lenses have a good development potential. Keywords: Oxygen permeability, contact lenses, silicone hydrogel, sol-gel, light polymerization

Purpose: To examine the variables that influence lipid deposition on conventional and silicone hydrogel contact lens materials and to build a physiologically relevant in vitro model of lipid deposition on contact lenses. Methods: Lipid deposition on contact lens materials can lead to discomfort and vision difficulty for lens wearers. Using a variety of radiochemical experiments and two model lipids (cholesterol and phosphatidylcholine), a number of clinically significant parameters that may influence lipid deposition were examined. • The optimization and characterization of a novel artificial tear solution (ATS) was examined (Chapter 3) • Optimization of an extraction system to remove deposited cholesterol and phosphatidylcholine from various contact lens materials (Chapter 4) • The influence of different tear film components on lipid deposition was researched (Chapter 5) • The efficiency of hydrogen peroxide disinfecting solutions to remove deposited lipid from contact lenses was investigated (Chapter 6) • The effect of intermittent air exposure on lipid deposition was examined through the use of a custom built “model blink cell” (Chapter 7) Results: A novel complex ATS designed for in-vial incubations of contact lens materials was developed. This solution was stable and did not adversely affect the physical parameters of the contact lenses incubated within it. An efficient extraction protocol for deposited cholesterol and phosphatidylcholine was optimized based on chloroform and methanol with the addition of water and acetic acid for phosphatidylcholine extraction. Overall, cholesterol and phosphatidylcholine deposition is cumulative over time and found to deposit in greater masses on silicone-containing hydrogels. Cholesterol and phosphatidylcholine deposition is influenced by the composition of the incubation medium and air exposure which occurs during the inter-blink period. Hydrogen peroxide disinfecting solutions were able to remove only marginal amounts of lipid from the contact lenses, with the surfactant containing solution removing more. Conclusion: This thesis has provided hitherto unavailable information on the way in which lipid interacts with conventional and silicone hydrogel contact lens materials and the in vitro model built here can be utilized in various ways in the future to assess other aspects and variables of lipid and protein deposition on a variety of biomaterials.

碩士
逢甲大學
科技管理碩士學位學程
107
In recent years, the proportion of myopia population in Taiwan has continued to rise. Improperly, 3C products and living habits have caused problems in the eyesight of Chinese people, and the age group of myopia has continued to decline. As teenagers and young children are more exposed to 3C products, the ratio of myopia is caused. Continued to rise, in response to advances in technology, myopia is no longer only the choice of glasses as the only corrective choice, more and more people choose contact lenses to wear, most customers for aesthetics, comfort or convenience, so The products have won the hearts of many users, and have become the target of the industry's opponents to imitate learning and transcendence. In the face of such a highly competitive market at home and abroad, in recent years, patents are also the areas in which the four major players in the industry compete. There are always litigations that tell each other that they infringe on their own technology, especially the amount of litigation in the water gel. Therefore, this study will focus on the patented aspects of contact lens hydrophobic glue, using the technology life cycle classification, combined with TRIZ theory, to understand what are the difficulties of this technology at the current stage, what breakthroughs can be made, those can be redeveloped, can give this industry This technology can be used in the future to make recommendations for research and development.

碩士
中原大學
醫學工程研究所
97
Silicone hydrogel contact lenses are new generation contact lenses because of its high oxygen permeability and low protein adsorption, which could increase comfort during wear. These characteristic properties are all attributed to the surface properties of silicone hydrogel. The purpose of this study was to evaluate the effects of 3-(methacryloyloxypropyl)-tris(trimethylsiloxy)silane (TRIS) on the surface properties of silicone hydrogels. In addition, polyvinyl pyrrolidone (PVP) was employed as a surface wetting agent and its effect on the surface hydrophobicity of silicone hydrogel was observed. The silicone hydrogel membrane consisted of 2-hydroxyethyl methacrylate, N,N-dimethylacryl amide, ethylene glycol dimethacrylate and TRIS monomers. In the first part of this study, it was found that the modulus increased from 0.22 MPa to 4.61 MPa as the amount of TRIS increased from 15 to 45 mol%. In addition, the oxygen permeability (DK) of the silicone hydrogel membrane increased from 60 to 110 barrers and the water content decreased from 48% to 13% given the same conditions. Based on these results, a ternary phase diagram was plotted. On the other hand, the second part of this study showed that the wetting agent PVP can notably decrease the contact angle of the membrane from 90o to 78o, bringing its value close to that of conventional contact lenses. In the third part of this study, it was found that significantly low protein adsorption on the membrane was obtained. However, increased membrane adsorption of lipid was found as the TRIS content increased. Lastly, the in vitro cytotoxicity tests showed that the silicone hydrogel and the conventional contact lenses are of the same 1 class according to ASTM F-895 standard. In conclusion, the present study reports various surface properties as a function of the composition of silicone hydrogel. This study suggests that the selection of the TRIS composition depends on a compromise between Dk and the water content of the silicone membranes. Furthermore, a surface wetting agent may be used with silicon hydrogel so as to avoid dry-eye symptom.