Influence of base and photoacid generator on deprotection blur in extreme ultraviolet photoresists and some thoughts on shot noise

A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the wt % of base and photoacid generator (PAG) were varied. A six times increase in base wt % is shown to reduce the size of successfully patterned 1:1 line-space features from 52 to 39 nm without changing deprotection blur. Corresponding isolated line edge roughness is reduced from 6.9 to 4.1 nm. A two times increase in PAG wt % is shown to improve 1:1 line-space patterning from 47 to 40 nm without changing deprotection blur or isolated line edge roughness. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photogenerated acids in the resists that have been studied. © 2008 American Vacuum Society

Cytomegalovirus infection of the upper gastrointestinal tract following liver transplantation—incidence, location, and severity in cyclosporine- and FK506-treated patients

One hundred and forty randomly selected liver transplant recipients were studied before and after primary orthotopic liver transplantation for the presence or absence of CMV enteritis. Following OLTx, 65 patients were treated with cyclosporine A and 75 were treated with FK506. The two groups were similar with regard to the incidence, location, and outcome of their upper gastrointestinal CMV infection. Prior to OLTx, only one patient had evidence of enteric CMV infection. The incidence of CMV enteritis post-OLTx was 27.7% in the CsA-treated group and 20% in the FK-treated group. During the first posttransplant month, no patient in the FK-treated group developed CMV enteritis, compared with 11.5% of the patients who were treated with CsA (P<0.05). Gastric CMV was found in over 80% of those positive for any organ in either group. In addition to CMV infection of the upper gastrointestinal tract, clinically evident CMV disease involved more nonenteric organs in the CsA-treated group than in the FK-treated group. In the CsA-treated group, CMV-negative patients had a statistically higher 1-year survival rate (100%) than CMV-positive patients (77.8%) (P<0.05). In the FK-treated group, no difference in survival was observed between CMV-positive or CMV-negative cases at 1 year. Of the patients on CsA, 20% received OKT3 for persistent rejection, as compared with 13% in the FK-treated group. The patients receiving both CsA and OKT3 had a higher rate of upper gastrointestinal CMV infection than did FK-treated patients who also received OKT3 therapy (38.5% versus 20%, respectively). Based upon these data, it can be concluded that (1) patients receiving FK have a lower incidence of enteric CMV infection; (2) following OLTx, upper gastrointestinal CMV infection presents later in FK-treated patients; (3) the stomach is the most frequently involved organ in the UGIT; (4) FK-treated liver recipients have less severe enteric CMV infection than do CsA-treated patients; (5) enteric CMV is not a major cause of mortality in liver trans lant recipients; and (6) in patients receiving FK, those who require OKT3 therapy do not appear to be at a greater risk for the development of CMV enteritis than those who do not. © 1992 by Williams & Wilkins

One Dimensional Coordination Polymers with Molecular Recognition Capability as Dynamic and Multifunctional Materials

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Inorgánica. Fecha de lectura: 07-04-2016La presente tesis doctoral se ha realizado en el grupo de Nanomateriales en el Departamento de Química Inorgánica de la Universidad Autónoma de Madrid. En la presente tesis, hemos diseñado, sintetizado, y caracterizado nuevos polímeros de coordinación con propiedades multifuncionales, en particular, propiedades eléctricas, magnéticas, y fotoluminiscentes, y que además muestran carácter dinámico (materiales de tipo estímulo-respuesta).Esta tesis está dividida en cinco capítulos; introducción general a polímeros de coordinación y los objetivos de la tesis (capítulo 1), los resultados y discusión de los mismos (capítulos 2 y 3), conclusiones (capítulo 4), y la sección experimental (capítulo 5). Los resultados y las discusiones se han presentado en capítulos 2 y 3, dependiendo de los bloques de construcción de partida, centros metálicos y ligandos orgánicos, que han sido usados para preparar los complejos de coordinación. A este respecto, el capítulo 2 incluye las interacciones de nucleobases modificadas, timina-1-ácido acético (TAcOH) y uracilo-1-ácido acético (UAcOH), como ligandos orgánicos, y metales de transición, Cu y Co, como centros metálicos. Las reacciones directas entre estos dos bloques de construcción nos permiten separar varios complejos variando desde mononucleares hasta 1D-CPs. Por otra parte, en el capítulo 3 se exponen las interacciones de sales de Cu(I) con ligandos de derivados de piridina, 2-amino-5-nitropiridina, etil-isonicotinato (EtIN), y ácido isonicotínico (INH). Las reacciones directas entre estos dos bloques de construcción nos permiten separar una familia de 1D-CPs de formula [CuX(L)]n, .donde X es un haluro, y L el ligando derivado de piridina. Por último, las nanoestructuras de unos polímeros de coordinación se han obtenido y se han estudiado sus posibles aplicaciones nanotecnológicas en el sector biomédico.The present thesis doctoral has been realized in Nanomaterials group at Department of Inorganic Chemistry, University Autonomous of Madrid. In the present thesis, we designed, synthesized, and characterized new coordination polymers with multifunctional properties, in particular electrical, magnetic, and photoluminescent properties, and show dynamic character (stimuli responsive materials). This thesis is divided into five chapters; general introduction to coordination polymers and the objectives of the thesis (chapter 1), the results and discussions (chapters 2 and 3), conclusions (chapter 4), and experimental section (chapter 5). The results and discussions have been presented in chapters 2 and 3, depending on the starting building blocks, metals centres and organic ligands, which have been used to prepare the coordination complexes. Chapter 2 includes the interactions of modified nucleobases, thymine-1-acetic acid (TAcOH) and uracil-1-acetic acid (UAcOH), as organic ligands, and transition metals, Cu, and Co, as metal centres. The direct reactions between these two building blocks allow us to separate several complexes ranged from mononuclear to extended 1D-CPs. On the other hand, chapter 3 involves the interaction between Cu(I) salts with selected pryidine derivative ligands, 2-amino-5-nitropyridine, ethyl-isonicotinate (EtIN), and isonicotinic acid (INH). The direct reactions between these two building blocks allow us to separate extended 1D-CPs formulated as [CuX(L)]n where X = halides, and L = pryidine derivative ligands. Finally, nanostructures of few coordination polymers have been obtained and we explore their nanotechnological application in biomedical sector

Temporal resolution of cell death signaling events induced by cold atmospheric plasma and electroporation in human cancer cells

Cancer treatment resistance and their invasive and expensive nature is propelling research towards developing alternate approaches to eradicate cancer in patients. Non-thermal, i.e., cold atmospheric plasma (CAP) and electroporation (EP) applied to the surface of cancerous tissue are new methods that are minimally invasive, safe, and selective. These approaches, both independently and synergistically, have been shown to deplete cancer cell populations, but the signaling mechanisms of death and their timelines of action are still widely unknown. To better understand the timeframe of signaling events occurring upon treatment, human cancer cell lines were treated with CAP, EP, and combined CAP with EP. The stages and incidence of apoptosis were tracked through time via flow cytometry while the activation/inactivation of the penultimate apoptotic signaling complex was examined through real-time fluorescent imaging. These treatments represent a promising new therapy in the global fight against cancer

Effect of Helium Ions Energy on Molybdenum Surfaces Under Extreme Conditions

Plasma facing components (PFCs) in fusion devices must be able to withstand high temperatures and erosion due to incident energetic ion radiations. Tungsten has become the material of choice for PFCs due to its high strength, thermal conductivity, and low erosion rate. However, its surface deteriorates significantly under helium ion irradiation in fusion-like conditions and forms nanoscopic fiber-like structures, or fuzz. Fuzz is brittle in nature and has relatively lower thermal conductivity than that of the bulk material. Small amounts of fuzz may lead to excessive contamination of the plasma, preventing the fusion reaction from taking place. Despite recent efforts, the physical mechanism of the surface deterioration is still not clear. This necessitates finding alternative materials for PFCs. In this report, the effect of helium ion energy on molybdenum surfaces is investigated. Helium ion irradiations on mirror finished polished molybdenum samples are performed as a function of helium ion energy from 100-1600eV with fixed values of ion-flux (7.2 x 1020 ions m-2 s-1), ion-fluence (2.6 x 1024 ions m-2), and temperature (923K). The surface modifications were studied using scanning electron and atomic force microscopy along with X-ray photoelectron spectroscopy and optical-reflectivity measurements. Reduction in the “protrusion” of fuzz from the surface and fuzz density at increased energy have been seen from microscopy and optical reflectivity studies. These findings further the understanding of fuzz formation on high-Z refractory metals for fusion applications. KEYWORD

Structural Evolution of Tungsten Surface Exposed to Sequential Low-Energy Helium Ion Irradiation and Transient Heat Loading

Structural damage due to high flux particle irradiation can result in significant changes to the thermal strength of the plasma facing component surface (PFC) during off-normal events in a tokamak. Low-energy He+ ion irradiation of tungsten (W), which is currently the leading candidate material for future PFCs, can result in the development of a fiber form nanostructure, known as “fuzz”. In the current study, mirror-finished W foils were exposed to 100 eV He+ ion irradiation at a fluence of 2.6 × 1024 ions m−2 and a temperature of 1200 K. Then, samples were exposed to two different types of pulsed heat loading meant to replicate type-I edge-localized mode (ELM) heating at varying energy densities and base temperatures. Millisecond (ms) laser exposure done at 1200 K revealed a reduction in fuzz density with increasing energy density due to the conglomeration and local melting of W fibers. At higher energy densities (∼ 1.5 MJ m−2), RT exposures resulted in surface cracking, while 1200 K exposures resulted in surface roughening, demonstrating the role of base temperature on the crack formation in W. Electron beam heating presented similar trends in surface morphology evolution; a higher penetration depth led to reduced melt motion and plasticity. In situ mass loss measurements obtained via a quartz crystal microbalance (QCM) found an exponential increase in particle emission for RT exposures, while the prevalence of melting from 1200 K exposures yielded no observable trend

Effect of Dual Ion Beam Irradiation (Helium and Deuterium) on Tungsten–Tantalum Alloys Under Fusion Relevant Conditions

The selection of tungsten (W) as a divertor material in ITER is based on its high melting point, low erosion, and strong mechanical properties. However, continued investigation has shown W to undergo severe morphology changes in fusion-like conditions. Recent literature suggests alloying W with other ductile refractory metals, viz. tantalum (Ta) may resolve some of these issues. These results provide further motivation for investigating W–Ta alloys as a plasma-facing component (PFC) for ITER and future DEMO reactors. Specifically, how these alloy materials respond to simultaneous He+ and D+ ion irradiation, and what is the effect on the surface morphology when exposed to fusion relevant conditions. In the present study, the surface morphology changes are investigated in several W–Ta targets (pure W, W-1%Ta, W-3%Ta, and W-5% Ta) due to simultaneous He+ and D+ ion irradiations. This comprehensive work allows for deeper understanding of the synergistic effects induced by dual ion irradiation on W and W–Ta alloy surface morphology. Pure W and W–Ta alloys were irradiated simultaneously by 100 eV He+ and/or D+ ions at various mixture ratios (100% He+, 60% D+ + 40% He+, 90% D+ + 10% He+ ions and 100% D+ ions), having a total constant He fluence of 6 × 1024 ion m−2, and at a target temperature of 1223 K. This work shows that slight changes in materials composition and He/D content have significant impact on surface morphology evolution and performance. While both the pure W and W–Ta alloys exhibit very damaged surfaces under the He+ only irradiations, there is a clear suppression of the surface morphology evolution as the ratio of D+/He+ ions is increased

Investigating Tantalum as a Plasma-Facing Component for Nuclear Fusion Reactors

Nuclear fusion is a potential source for producing unlimited environment-friendly energy. Tungsten (W) is selected as the primary candidate material for plasma facing component in nuclear fusion reactors due to its high melting temperature (3695 K), low sputtering erosion yield and strong mechanical properties. However, recent investigations on W have confirmed that it undergoes severe surface morphology changes during low energy He plasma and/or ion irradiation similar to a harsh fusion environment. Additionally, our previous studies indicate that tantalum (Ta) may show better resistance to the harsh radiation environment and is therefore worthy of investigation. Hydrogen retention properties, specifically deuterium (D) retention in Ta, are not well documented and are extremely important safety issue for fusion reactors. Consequently, we exposed Ta to a fusion-like environment of low-energy D ions and performed thermal desorption spectroscopy (TDS). Then, the samples were rapidly loaded (to avoid possible surface oxidation) into another vacuum chamber where we performed the thermal desorption spectroscopy measurements. Our investigations indicate two binding energy values for D in Ta, i.e. 1.8 eV and 2.1 eV. We observe a higher binding energy and a higher retention rate for D in Ta than W. We also observed that our results are consistent with theoretical predictions based on the absorption of D in Ta. Our preliminary results indicate that Ta shows better resistance to nanostructure formation (fuzz) than W in a fusion environment. However, this is still an open question and part of ongoing investigations

Fluence Dependent Surface Modification on Tungsten Coatings Using Low Energy Helium Ion Irradiation at Elevated Temperatures

Nuclear fusion is the most promising renewable energy source for the near future. It can provide a large amount of energy using a very small amount of fuel, as compared with that of the coal, oil, or nuclear fission. The chain reaction in nuclear fusion produces the energy and fuel, from hydrogen isotopes available in see water. Tungsten (W) is a leading candidate material for the plasma-facing component (PFC) in nuclear fusion reactors such as ITER (international thermonuclear experimental reactor), because of its high melting point, high yield strength, low erosion and low hydrogen isotope retention. Recent studies showed deeply convoluted fiber-form nanostructures (fuzz) formation on W surface under high-flux low-energy He+ irradiation relevant to fusion conditions. The fuzz greatly degrades the mechanical, thermal, and optical properties of W. The significant enhanced surface area, and fragility of such fuzz, raise several serious concerns for its usefulness as PFC materials in fusion reactors. The fuzz can also be easily eroded and is a major concern for plasma contamination and short lifetime. In this study, we report on the effect of helium ion irradiation on the surface morphology evolution of W exposed to low energy He+ ions at constant elevated temperature. Submicron thickness W films were deposited on Silicon (100) at room temperature using RF sputtering deposition technique. Several samples were cut and were exposed to 100 eV He+ ions having a constant flux of 1.2 × 1021 ions m−2 s−1 and sample temperature (1173K). The fluence was varied in the range of 4.3 × 1024 – 1.7 × 1025 ions m−2. Post ion-irradiation samples (including pristine) were characterized using field emission scanning electron microscopy (FE-SEM), X-ray photoelectric spectroscopy (XPS), and optical reflectivity measurements for monitoring the changes in surface morphology, chemical composition, and surface roughness/optical properties, respectively. We observed a sequential enhancement in the W fuzz density, sharpness, and protrusions from the film surface, with increasing helium ion fluence. Ex-situ XPS study shows the evidence of W2O3 phase formation due to natural oxidation of W fuzz in the open atmosphere. The study is also relevant to potential applications in solar power technology and in water splitting for hydrogen production