Monitoring of the plasma generated by a gas-puff target source

A 10-Hz repetition rate, Nd:YAG pulsed laser (\ensuremath{\lambda}=1064\text{ }\text{ }\mathrm{nm}, pulse energy of 0.69 J, pulse duration of 3 ns) irradiated a Xe double-stream gas-puff target source. The interaction gives rise to the formation of plasma and emission of soft x-ray and extreme ultraviolet radiation. The produced plasma was investigated and characterized by a silicon carbide (SiC) and a commercial silicon (Si) detector, applying different spectral filters. Some parameters such as the plasma stability and its evolution (time trace profile and pulse time duration) are presented and discussed, evidencing pros and cons of the employment of SiC detectors with respect to the traditional Si for laser-generated plasma diagnostic

Nitrogen doping in biomaterials by extreme ultraviolet (EUV) surface modification for biocompatibility control

Various studies show that employment of nitrogen coatings on certain biomaterials can noticeably increase the degree of biocompatibility (particularly for vascular repair) [1]. Chemical and laser ablation surface modification techniques are used for introduction or enrichment of nitrogen. However alteration of bulk material is reported which is undesirable for biomedical engineering applications. Extreme Ultraviolet (EUV) radiation with low penetration depth (less than 100 nm) can be successfully utilized to avoid bulk properties alteration. In this study Polyvinyl fluoride (PVF) and Polytetrafluoroethylene (PTFE) were treated by EUV radiation in the presence of ionized nitrogen. X-ray photoelectron spectroscopy (XPS) measurements demonstrate a notable amount of nitrogen on treated polymer surfaces

Polycarbonate polymer surface modication by extreme ultraviolet (EUV) radiation

The degree of the biocompatibility of polycarbonate (PC) polymer used as biomaterial can be controlled by surface modification for various biomedical engineering applications. In the past, PC samples were treated by excimer laser for surface reorganization however associated process alteration of bulk properties is reported. Extreme ultraviolet radiation can be employed in order to avoid bulk material alteration due to its limited penetration. In this study, a 10 Hz laser-plasma EUV source based on a double-stream gas-pu_ target irradiated with a 3 ns and 0.8 J Nd:YAG laser pulse was used to irradiate PC samples. The PC samples were irradiated with different number of EUV shots. Pristine and EUV treated samples were investigated by scanning electron microscopy and atomic force microscopy for detailed morphological characterization of micropatterns introduced by the EUV irradiation. Associated chemical modifications were investigated by X-ray photoelectron spectroscopy. Pronounced wall-type micro- and nanostructures appeared on the EUV modified surface resulting in a change of surface roughness and wettability

Surface structuring and wettability control of Polyvinyl fluoride (PVF) using extreme ultraviolet (EUV) surface modification.

In this study, surface modification of fluoropolymer Polyvinyl fluoride (PVF) films was performed using Extreme Ultraviolet (EUV) radiations to induce patterned structures on surface and to provide control over the surface wettability. Specially developed laser produced plasma based EUV source was used for surface structuring. The double stream gas-puff target was produced by injection of krypton and xenon (KrXe) gas mixture into a hollow stream of helium. Commercially available EKSPLA Nd:YAG 1.06 micron laser was used to irradiate the KrXe gas puff target with 3 nanosecond pulse duration having 0.8 J energy. The PVF films were irradiated with 50 and 200 EUV pulses. The surface characterisation of the pristine and EUV modified PVF polymer films was performed by Atomic Force Microscopy (AFM) for morphological modifications. To investigate chemical modifications, X-ray Photoelectron Spectroscopy was used. The wettability of the sample surfaces was examined by Water Contact Angle (W CA) measurements. EUV surface modification of PVF films resulted in formation of wall type rippled structures on the polymer surfaces. The surface roughness of the EUV treated surfaces was increased up to 287 nm and 21° reduction was observed in the WCA of the PVF films. Successful surface structuring and wettability control was obtained using EUV surface modification of PVF films

Plasma characterization of the gas-puff target source dedicated for soft X-ray microscopy using SiC detectors

Abstract An Nd:YAG pulsed laser was employed to irradiate a nitrogen gas-puff target. The interaction gives rise to the emission of soft X-ray (SXR) radiation in the 'water window' spectral range (λ= 2.3÷4.4 nm). This source was already successfully employed to perform the SXR microscopy. In this work, a Silicon Carbide (SiC) detector was used to characterize the nitrogen plasma emission in terms of gas-puff target parameters. The measurements show applicability of SiC detectors for SXR plasma characterization

A stand-alone compact EUV microscope based on gas-puff target source

We report on a very compact desk-top transmission extreme ultraviolet (EUV) microscope based on a laser-plasma source with a double stream gas-puff target, capable of acquiring magnified images of objects with a spatial (half-pitch) resolution of sub-50 nm. A multilayer ellipsoidal condenser is used to focus and spectrally narrow the radiation from the plasma, producing a quasi-monochromatic EUV radiation (λ = 13.8 nm) illuminating the object, while a Fresnel zone plate objective forms the image. Design details, development, characterization and optimization of the EUV source and the microscope are described and discussed. Test object and other samples were imaged to demonstrate superior resolution compared to visible light microscopy. Lay description Developments in nanoscience demand tools capable of capturing images with a nanometer spatial resolution beyond the capability of well-known visible light microscopes. Herein, we present the design details, development, characterization and optimization of a very compact desk-top transmission microscope, operating in invisible to an eye radiation from the so called extreme ultraviolet (EUV) range. The apparatus is based on a laser-plasma source coupled with a special type of objective called Fresnel zone plate. It is capable of acquiring magnified images of objects with a spatial resolution of sub-50 nm, approximately 5–10 times better than the spatial resolution of classical visible light microscopes, in a short acquisition time. The main motivation for development of such compact systems operating with EUV radiations is the possibility to get information about thin samples due to the easily absorption of these radiation by solid materials with very small thicknesses, of the order of about 100 nm. Additionally, the employment of such kind of microscopes might open the possibility to perform experiments without necessity to employ large ‘photon facilities’ such as synchrotrons or free electron lasers and could have a huge impact on the speed of nanotechnology development. Imaging results, concerning nanostructures and biomedical samples, are presented and discussed

Swelling of biocompatible polymer films.

The incorporation of drugs into phosphorylcholine (PC) polymers coated onto coronary stent surfaces is one potential method of treatment for reducing restenosis, the reclosure of the artery after angioplasty treatment. This work on the characterisation of the swelling performance of thin PC polymer films represents a further extension of the study on biocompatible polymers. The broad aim of this work is to relate the PC polymer structure and film processing conditions to their swelling, drug loading and release kinetics. As the two highly sensitive and powerful techniques in film structure determination, both ellipsometry and neutron reflection have proved to be useful in characterising PC polymer films and drug release processes. Following an established ellipsometry measurement method, a two stage process consisting of diffusion and relaxation has been observed during the PC film swelling: this suggests an anomalous mechanism, and this performance is well described by the coupled diffusion and relaxation model developed by Berens and Hopfenberg. Furthermore, the swelling of PC polymer films was investigated as a function of cross-linking, annealing temperature, chemical composition, hydrophilic/hydrophobic ratios, film thickness and environmental conditions by ellipsometry measurements, and their effects on swelling kinetics well quantified. The structures of the PC polymer films (PC100B) with cross-linking groups have been further characterised by neutron reflection. The segregation of hydrophobic and hydrophilic domains was found in the PC films with different dimensions. The PC100B with deuterated dodecyl chains was used to highlight the interfacial structures of the PC films. The hydrophilic segments, including phosphorylcholine groups and hydroxypropyl groups, are preferentially adsorbed at the polymer/substrate interface. The hydrophobic dodecyl chains are expelled away from the silicon oxide surface. The main part of PC100B films is the middle uniform region with 40% of water in the sample annealed at 150°C, and 55% of water in the sample annealed at 50°C. The combination of the ellipsometry results and the drug release profiles from UV measurements indicates that the drug release pattern is strongly affected by the film swelling kinetics when the drug molecules and polymer matrix interact weakly. Otherwise, a strong interaction between the drug and the polymer will dominate the drug release behaviour from the PC polymer films