Cip-Data Library Technische Universiteit Eindhoven

Organic Optoelectronics and Photonics II, 2006

The gravure printing technique is currently under investigation as a possible method for the roll-to-roll production of OLEDs in the 6th framework EU funded project entitled ROLLED -"Roll-to-roll manufacturing technology for flexible OLED devices and arbitrary size and shape displays". The objective in the project is to fabricate an entire OLED structure by using roll-to-roll manufacturing methods and to examine, how the commercial production could be set up and integrated into an existing printing process. In order to attain a roll-to-roll compatibility, all the materials, inks and device structures need to be suitable for printing. Since, such OLED device structures are very sensitive to moisture and oxygen, high barrier materials to be applied as wet chemical coatings on transparent polymer films such as PET by common roll-to-roll coating techniques have been investigated. The barrier films on their respective substrates act as front and back side encapsulation materials, where the front side encapsulation material is to be used as a transparent and flexible substrate for OLED fabrication. The transmission rates to be achieved for both front and back side encapsulation for oxygen and water vapour are 5 mg m -2 day -1 (corresponding to 7 cm³ m -2 day -1 for O 2 ). In this paper, we show how light-emitting devices manufactured by gravure printing operate compared to the ones manufactured by traditional methods. Furthermore, we present recent results on the development of ITO nanoparticle coatings, cathode inks and flexible barrier materials.

Optical Materials, 2017

A major problem hindering the development of diffractive optics and micro-and nanoelectronics is how to fabricate surfaces with the desired degree of cleanliness. Residual resist layers as well as organic molecular compounds (solvents, chemicals, etc.) adsorbed at wafer surfaces are the primary sources of contamination [160,161]. This necessitates cleaning organic contaminants off substrate surfaces before etching. Today, the most common surface-cleaning techniques are chemical cleaning, laser cleaning, and plasma cleaning. To generate uniform plasma, plasma techniques use high-frequency (HF) and superhigh-frequency (SHF) sources that are complex, costly, and energy-intensive. Treating wafers with plasma generated by such sources contaminates surfaces with low-active or inactive particles because the substrate is placed between the electrodes of the gas-discharge device. Plasma parameters in this case are determined chiefly by the properties of the surface being treated (the loading effect). Chapter 1 demonstrated the advantages of using off-electrode plasma. In that technique, ion-plasma fluxes are formed outside the electrodes, and the possibility of the surface becoming contaminated with inactive plasma particles is ruled out because only negatively charged particles (ions and electrons) move toward the surface. But because contemporary literature is silent on theoretical and experimental research into the mechanism of surface cleaning that uses off-electrode plasma, no practical methods are yet available. This chapter analyses widely used conventional cleaning techniques and theoretically and experimentally investigates the mechanism of surface cleaning with directed fluxes of low-temperature plasma generated by a high-voltage gas discharge outside the electrode gap. The discussion is aimed at creating efficient cleaning methods to improve the fabrication quality of optical microreliefs.

Bonded direct and indirect restorations have become the appropriate choice in many clinical situations where conservation of tooth structure and esthetics are paramount. Inadequate polymerization is known to have deleterious effects on resin bonded restorations such as tooth sensitivity, microleakage, fractures or complete debonding of restorations. Quartz-tungsten-halogen (QTH) units have been widely used for polymerizing resin-based dental materials for decades. However, QTH lamps exhibit several shortcomings, which is probably why the lightemitting diode (LED) polymerization lights were introduced as the alternative means for polymerizing light cured restorations. Some drawbacks of Quartz-tungsten-halogen technology have been reviewed in this paper, together with several important properties associated with LED polymerization lights and dental materials treated using LED technology, such as depth of cure and hardness. Kratak sadržaj Direktne i indirektne "bonded" restauracije zuba su indikovane u mnogim kliničkim situacijama, gde je očuvanje strukture zuba i estetike od vrhunskog značaja. Dokazano je da neadekvatna polimerizacija ima štetan uticaj na restauracije smolama, koji se ogleda u osetljivosti zuba, mikro curenju, frakturi ili potpunom odvajanju restauracije. Kvarctungsten-halogenske (QTH) lampe su već decenijama u širokoj upotrebi za polimerizaciju stomatološkim materijalima na bazi smola. Međutim, QTH lampe imaju i nekoliko nedostataka, što je verovatno i razlog zbog čega je LED polimerizaciona svetlost uvedena kao alternativno sredstvo za ove restauracije. Ovaj rad obrađuje dubinu polimerizacije i tvrdoću, važne karakteristike stomatoloških materijala koji se tretiraju upotrebom LED tehnologije.

International polymer science and technology, 2005

2003

Third International Symposium on Laser Precision Microfabrication, 2003

In this paper some recent results are presented about the photochemical modification of polymers by UV-laser-irradiation which leads to a controllable and local change of the refractive index in the irradiated area of the polymer surface. The exact modification mechanism and its relation to the modified refractive index have been investigated on the basis of PMMA used as a UV-modifiable model polymer with good optical quality. This new UV-laser-assisted technology for photochemical modification of the optical properties of UV-modifiable polymers like PMMA or PMMI and their fluorinated derivates permits the fabrication of a wide range of integrated-optical components like strip waveguides, power splitters, (Mach-Zehnder-)interferometers, Bragg gratings and other dispersive structures. These integrated-optical elements are crucial for the realization of dispersive componentes like WDM or AWG, which have a wide application in the optical sensor and information technology. The optical and functional properties like loss rate or mode propagation of some selected integrated-optical components have been investigated and are discussed in this article.

2004

The combination of direct-write techniques with the deposition of sol-gel films has the opportunity of creating low-cost optical components. Recent advancements in both fields suggest the possibility of fabricating novel components for rapid prototyping purposes. This paper presents continuing work in the integration of these two concepts for the development of a novel manufacturing process. The results concentrate on laser processing stage, as well as on the optical characterization of simple waveguides. 1. Project Summary: The recent increase in demand for information bandwidth has created the need for improving current technologies for data, voice and video transmission. New technologies have emerged addressing different aspects of networking, such as transmission protocols, communication devices, and manufacturing methods of these devices. Two particular areas of interest in the advancement of ultrahigh capacity optical networks include function integration in optoelectronic com...

2010

Versatile direct laser writing (DLW), not limited by material photosensitivity, offers opportunities for fundamental and technological innovation for micro-/nanofabrication in integrated photonics, electronics and material science. Although DLW has high potential in micro-/nanodevice fabrication, material choice suffers an intrinsic limitation: DLW cannot be applied to non-photosensitive materials. We describe a newly discovered rapid-assembly phenomenon of fine particles based on femtosecond laser multi-photon-reduction in solution. this phenomenon allowed the writing of micropatterns with thick clad layers filled with nanoparticles. We wrote continuous patterns by moving the laser focus even in the case of non-photosensitive material such as Sio 2. By transcending the strict material limitation, this novel laser writing process promises to be a powerful tool in a variety of scientific fields. Versatile direct laser writing (DLW), not limited by material photosensitivity, offers the possibility of true photo-fabrication of highly functional micro-/nanodevices, which is of interest in various fields such as nanophotonics, electronics, material science and life science. DLW is a simple and rapid fabrication process for various micro-/nanostructures based on light-matter interaction including photo-polymerisation, photo-reduction, sintering, lattice defect formation, phase separation and carbonization 1-6. Micro-/nanostructures can be written only by translating a laser focus. Compared to DLW, conventional lithographic fabrication requires complicated and repetitive processes such as vacuum deposition and plasma etching. So far, many groups have reported DLW of Ag, Au, Cu, photopolymers, carbon, photosensitive glasses, modified polydimethylsiloxane and so on 7-15. Although it has succeeded in the formation of functional structures for nanophotonic devices 16-20 , super capacitors 21 , microactuators 22 , superhydrophobic surfaces 23 , and bio-scaffolds 24,25 , the technique typically encounters an intrinsic material limitation. That is, DLW cannot be applied to materials without photosensitivity. Adequate optical responses to light sources are essentially required in target materials. In one use case, Ag micropatterns can be directly formed by laser irradiation of visible wavelength to Ag nano-ink 26. In this process, laser light is absorbed by Ag nanoparticles, followed by photothermal reactions to form the patterns. However, it is not easy to apply this laser setup to DLW of other materials such as different metals because these other targets do not necessarily have appropriate absorption properties and chemical reaction paths at this laser wavelength. That is, laser writing capabilities and properties including pattern size and height strongly depend on incident laser wavelength. From such a material limitation, it is also difficult to obtain SiO 2 micropatterns because of its high transmittance over a wide wavelength range. Therefore, vacuum UV photon such as F 2 laser (157 nm wavelength), which has photon energy higher than SiO 2 bandgap, is often required for glass processing 27,28. In another example, to write signal filters, so-called fiber Bragg gratings, inside optical fiber cores, KrF excimer laser of 248 nm wavelength is used because this wavelength fortunately matches an intrinsic absorption band of the fiber core materials 29,30. Such optimal irradiation ultimately allows for structural changes in Ge-related defects, resulting in refractive index changes and density modification at the irradiated region 4,30. Conversely, excessive absorption causes serious thermal damage just beneath the material surface because of the short penetration depth of light. Thus, an adequate overlap between laser oscillation wavelength and absorption band is a key factor for DLW. Of course, light-matter interactions can also be started by nonlinear optical absorption induced by ultrashort pulse laser 31-33. However, even for such cases, sufficient nonlinear responsivity and absorption intensity of materials is

Nature Photonics, 2007