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High-surface-quality amorphous carbon (a-C) optical coatings with a thickness of 45 nm, deposited by magnetron sputtering on a silicon substrate, were irradiated by the focused beam of capillary-discharge Ne-like Ar extreme ultraviolet laser (CDL=capillary-discharge laser; XUV=extreme ultraviolet, i.e., wavelengths below 100 nm). The laser wavelength and pulse duration were 46.9 nm and 1.7 ns, respectively. The laser beam was focused onto the sample surface by a spherical Sc/Si multilayer mirror with a total reflectivity of about 30%. The laser pulse energy was varied from 0.4 to 40 μJ on the sample surface. The irradiation was carried out at five fluence levels between 0.1 and 10 J/cm2, accumulating five different series of shots, i.e., 1, 5, 10, 20, and 40. The damage to the a-C thin layer was investigated by atomic force microscopy (AFM) and Nomarski differential interference contrast (DIC) optical microscopy. The dependence of the single-shot-damaged area on pulse energy makes it possible to determine a beam spot diameter in the focus. Its value was found to be equal to 23.3±3.0 μm using AFM data, assuming the beam to have a Gaussian profile. Such a plot can also be used for a determination of single-shot damage threshold in a-C. A single-shot threshold value of 1.1 J/cm2 was found. Investigating the consequences of the multiple-shot exposure, it has been found that an accumulation of 10, 20, and 40 shots at a fluence of 0.5 J/cm2, i.e., below the single-shot damage threshold, causes irreversible changes of thin a-C layers, which can be registered by both the AFM and the DIC microscopy. In the center of the damaged area, AFM shows a-C removal to a maximum depth of 0.3, 1.2, and 1.5 nm for 10-, 20- and 40-shot exposure, respectively. Raman microprobe analysis does not indicate any change in the structure of the remaining a-C material. The erosive behavior reported here contrasts with the material expansion observed earlier [L. Juha et al., Proc. SPIE 5917, 91 (2005)] on an a-C sample irradiated by a large number of femtosecond pulses of XUV high-order harmonics. [ABSTRACT FROM AUTHOR]

We have studied the feasibility of high-resolution laser interference lithography using a tabletop 46.9 nm, 1.5 ns Ar laser, combined with two different optical configurations based on a Lloyd’s mirror interferometer. Using one of these schemes we have encoded periodic grating structures with a half pitch of 42 nm and a vertical modulation of 5 nm on a commercial PMMA photoresist. Experiments performed with larger half-pitch structures and detailed theoretical calculations demonstrate the potentiality of producing periodic structures with a half-pitch resolution down to 20 nm and a height of up to 60 nm. The results can be of considerable interest for the development of a complete high-resolution lithographic process operating with the 47 nm laser wavelength. [ABSTRACT FROM AUTHOR]

Inverted surface plasmon resonance (ISPR) biosensors based on absorbent metal thin films with a graphene sheet on top are presented. Two systems have been examined by means of a numerical study, a bilayer of palladium/graphene and one of iridium/graphene. The features and performances of such biosensors are discussed. The proposed ISPR systems potentially disclose new strategies for high-resolution, sensitive and straightforward detection of multiple biomolecular interactions. [ABSTRACT FROM AUTHOR]

A prototype low cost table-top extreme ultraviolet (EUV) laser source (1.5 ns pulse duration, λ=46.9 nm) was successfully employed as a laboratory scale interference nanolithography (INL) tool. Interference patterns were obtained with a simple Lloyd’s mirror setup. Periodic structures on Polymethylmethacrylate/Si substrates were produced on large areas (8 mm2) with resolutions from 400 to 22.5 nm half pitch (the smallest resolution achieved so far with table-top EUV laser sources). The mechanical vibrations affecting both the laser source and Lloyd’s setup were studied to determine if and how they affect the lateral resolution of the lithographic system. The vibration dynamics was described by a statistical model based on the assumption that the instantaneous position of the vibrating mechanical parts follows a normal distribution. An algorithm was developed to simulate the process of sample irradiation under different vibrations. The comparison between simulations and experiments allowed to estimate the characteristic amplitude of vibrations that was deduced to be lower than 50 nm. The same algorithm was used to reproduce the expected pattern profiles in the λ/4 half pitch physical resolution limit. In that limit, a nonzero pattern modulation amplitude was obtained from the simulations, comparable to the peak-to-valley height (2–3 nm) measured for the 45 nm spaced fringes, indicating that the mechanical vibrations affecting the INL tool do not represent a limit in scaling down the resolution. [ABSTRACT FROM AUTHOR]

In this paper, an experimental set-up for the X-ray production (≈70 eV-25 keV energy range) by a plasma, obtained focalizing a high-power Nd:YAG laser beam on a specific target, is presented. The measures of the characteristics of a custom Nd:YAG high-power laser beam (maximum of 8 J at 1064 nm, 5 ns pulse duration) and a new disposition of the target-lens system in the interaction chamber are discussed. The aim of this research is the use of the plasma resulting by the focalization of the laser beam, which will be used as a soft X-ray source or an electron source instead of the hot filament of the standard mammographic X-ray tubes. [ABSTRACT FROM AUTHOR]

This article reports on the first utilization of the soft X-ray beamline at the DaΦne synchrotron light source for mapping the intake of different elements in plant tissues. As a test, the method of dual-energy X-ray microradiography was applied to the investigation of the natural sulfur content in dried leaf and root samples. Our ultimate goal was to monitor the pollutant lead and its intake, which was added in controlled doses to the hydroponic medium of laboratory-controlled samples of vegetal species. The results obtained by the nondestructive X-ray radiographic analysis are compared to the values of concentrations determined by a standard chemical analysis utilizing atomic absorption spectroscopy. From this comparison the validity of the X-ray detection of heavy metals in biological samples has been confirmed. The superposition of the dual energy results on the simple planar radiography shows the representation of the pollutant intake directly on the sample structures. It should be pointed out that this method, developed here for plant root and leaves could be applied to any biological sample of interest, but the preparation and observation conditions necessitate different strategies according to the type of sample under analysis. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The knowledge and the manipulation of light polarization state in the vacuum ultraviolet and extreme ultraviolet (EUV) spectral regions play a crucial role from materials science analysis to optical component improvements. In this paper, we present an EUV spectroscopic ellipsometer facility for polarimetry in the 90-160 nm spectral range. A single layer aluminum mirror to be used as a quarter wave retarder has been fully characterized by deriving the optical and structural properties from the amplitude component and phase difference δ measurements. The system can be suitable to investigate the properties of thin films and optical coatings and optics in the EUV region. [ABSTRACT FROM AUTHOR]