A. Bianco

Sincrotrone Trieste S.C.p.A., Trst, Friuli Venezia Giulia, Italy

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Publications (30)34.56 Total impact

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    ABSTRACT: The irradiation effects of multiple ultrafast shots of laser beams with estimated fluences of some tens of mJ/cm2 on a EUV Mo/Si multilayer have been studied. Irradiation damage has been induced by multiple shots of two different lasers (100 fs 400 nm the first, 1.5 ns 46.9 nm the second). The study has been motivated by the need of multilayer Mo/Si optics for the delay lines of the FEL source FERMI@Elettra, where these mirrors will be used to reflect 100 fs pulses at 13 nm with a fluence of some mJ/cm2. The analysis has been performed by means of different techniques as EUV and soft X-ray reflectivity, XPS, and Standing wave enhanced XPS. Simulations have been carried on by means of an indigenously developed software OPAL (Optical Properties of Anisotropic Layers) for the calculation of the absorbed energy by the stratified medium. AFM and SEM surface images have been also acquired. In the irradiation at 400 nm, we observed a significant change in the multilayer performance at fluences of 100 mJ/cm2 and above with a significant reduction of reflectivity. Spectroscopic analysis allowed to correlate the decrease of reflectivity with the degradation of the multilayer stacking, ascribed to Mo-Si intermixing at the Mo/Si interfaces of the first few layers, close to the surface of the mirror. Preliminary tests have been also performed on the sample irradiated at 46.9 nm.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2011; DOI:10.1117/12.886845 · 0.20 Impact Factor
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    ABSTRACT: We have investigated the damaging effects of a femtosecond pulsed laser beam with 400nm wavelength on a Mo/Si EUV multilayer. The exposures have been done in vacuum with multiple pulses (5pulses/mm2) of 120fs varying the laser fluence in the 38–195mJ/cm2 range. The analysis of the different irradiated regions has been performed ex-situ by means of different techniques, including specular and diffuse reflectivity, X-ray photoemission spectroscopy (XPS) and total electron yield (TEY) in the EUV and soft X-ray range. Surface images have been acquired by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results clearly indicate a progressive degradation of the EUV multilayer performances with the increase of the laser fluence. Spectroscopic analysis allowed to correlate the decrease of reflectivity with the degradation of the multilayer stacking, ascribed to Mo–Si intermixing at the Mo/Si interfaces of the first layers, close to the surface of the mirror.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2011; 635(1). DOI:10.1016/j.nima.2010.10.026 · 1.32 Impact Factor
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    ABSTRACT: The extensive upgrade of the experimental end-station of the SPECTROMICROSCOPY-3.2L beamline at Elettra synchrotron light source is reported. After the upgrade, angle-resolved photoemission spectroscopy from a submicrometre spot and scanning microscopy images monitoring the photoelectron signal inside selected acquisition angle and energy windows can be performed. As a test case, angle-resolved photoemission spectroscopy from single flakes of highly oriented pyrolitic graphite and imaging of the flakes with image contrast owing to rotation of the band dispersion of different flakes are presented.
    Journal of Synchrotron Radiation 07/2010; 17(4):445-50. DOI:10.1107/S0909049510013993 · 3.02 Impact Factor
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    ABSTRACT: FERMI@Elettra is a Free Electron Laser (FEL) user facility currently under construction at Sincrotrone Trieste, Italy. It will provide a spatial coherent transform-limited beam in the sub-ps regime, covering the wavelength range from 100 nm to 3 nm with the goal of 1 nm (by using third harmonics). The transform-limited beam is supposed to have a natural energy bandwidth of the order of 50-100 meV. Nevertheless, one of the three future beamlines, the one dedicated to Low Density Matter (LDM) studies, needs a monochromator to clean the signal. It must cover the whole wavelength range with eventual omission of the lower energy part. We will report the design of a fixed included angle monochromator employing three gratings. The optical system will be described, and particular attention will be given to the constraints like the pulse broadening, the focus displacement and, of course, the flux. Engineering constraints and manufacturers tolerances also taken into account will be presented, too.
    Advances in X-Ray/EUV Optics and Components IV; 09/2009
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    ABSTRACT: At the Elettra synchrotron light laboratory, a new undulator-based beamline with photon energy ranging from about 4.6 to 40 eV has been installed and opened to users. The beamline, based on a 4 m normal-incidence monochromator (NIM) with spherical gratings and movable exit slit, serves an end station to perform primarily high-resolution angle-resolved photoemission spectroscopy experiments in the low photon energy regime. The salient features of the instrument and some of the commission data are reported in this paper.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 07/2009; 606(3):780-784. DOI:10.1016/j.nima.2009.05.001 · 1.32 Impact Factor
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    ABSTRACT: The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the Sincrotrone Trieste laboratory in Trieste (Italy). It is a based on a seeded scheme that will provide an almost perfect transform limited beam and fully spatial coherent. It will cover the wavelength range from 100 to about 3 nm and in a short future down to 1 nm (by using higher harmonics). It is expected to be fully operative in the late summer of 2010. In this presentation we will report the layout of the photon beam diagnostics section with the preliminary tests, the radiation transport system to the experimental area, and the experimental hall facilities. A particular emphasis will be given to the optical solution and constrains due to the need of preserving the wave front and to avoid damage on the different optical elements, including slits, mirrors, gratings and all the diagnostic facilities. One of the main problems will be the necessity of using very large grazing incidence angle (up to 45°) on multilayers and single coating mirrors. These elements are mandatory to perform the transient grating experiments and to realize the delay lines, where time delay up to 1 nsec are required. This issue poses a serious problem in terms of energy density delivered and adsorbed by the optics and great care must be taken into the choice of the proper multilayer materials. Some studies on the reflectivity of multilayers and Carbon coated mirrors will be reported as well as the diagnostic tools to monitor the quality of the optics in operative conditions.
    Damage to VUV, EUV, and X-Ray Optics II; 05/2009
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    ABSTRACT: A natural application of the emerging technique of photoemission microscopy to the study of semiconductor interfaces is direct determination of heterojunction parameters by measuring the device in cross section. We present here results on p-n GaAs homojunctions, which served as a prototype system to demonstrate the applicability of this novel technique to buried semiconductor interfaces. We also describe preliminary measurements of the electrostatic potential profile across Al/GaAs Schottky junctions.
    01/2008: pages 121-130;
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    ABSTRACT: Even if not well defined a border exists between the soft and the hard X-ray region. The optics adopted in one region is not suitable for the other region and vice versa. Nevertheless, recently more and more experimentalists wish to investigate their samples by using an energy range as wide as possible. Without adopting complicated and very expensive mechanical solutions, it is a major challenge, for the optical designer, to find a solution suitable for both spectral ranges. This was our task for the TwinMic beamline at Elettra, the Italian 3rd generation synchrotron radiation source. This beamline will house a twin x-ray microscope, which combines scanning and full-field imaging in a single multipurpose end station and is operated in the 0.2-3 keV photon energy range. This energy range will be covered by a blazed grating, which has a very shallow blaze angle of 0.4°. With this grating mechanically ruled in the grating laboratory of Carl Zeiss very high diffraction efficiency can be achieved, expected to be higher then 10% over the whole range. This grating was tested at the KMC 1 beamline in BESSY, which is particularly suitable for this kind of measurements since it has a crystal monochromator that can go down to 1.7 keV and can be equipped with an high precision diffractometer. The obtained results demonstrate that it is possible to work with this grating up to 6 keV with still enough efficiency (5% at 6 keV and 15% at 1.8 keV). The efficiency in the lower part of the energy range was tested at Elettra, again with very good results (more then 20% at 950 eV and 15% at 600eV). A second grating, also produced by Carl Zeiss, with a blaze angle of 1.1° will be mounted in the same monochromator, to cover the lower energy range. Both gratings have 600 grooves/mm, which is a good compromise for achieving the requested energy resolving power (of the order of 4000 in most of the range) and to have as much flux as possible, mandatory for the experiments proposed for this beamline. A multilayer mirror, mounted side by side with the two gratings, will permit a wide band selection of the incoming radiation. The beamline is expected to be operative in spring 2007.
    01/2007; DOI:10.1063/1.2436107
  • G. Sostero, D. Cocco, A. Bianco
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    ABSTRACT: The interest of the scientific community in the use of synchrotron radiation has become higher and higher with the improvement of instrumentation and with publication of better and better results. For this reason, the concept of standard beamline could not be used anymore, and a lot of solutions must be considered to satisfy the requests of the different users. A very important part of these "solutions" involves mirrors, gratings and crystals adopted to carry out the light from the source to the experimental chamber. In the last years, for instance, we have seen an increased interest for the mechanically deformable mirrors, as well as normal incidence mirrors (for IR or UV photons). From the point of view of the optical metrology, this implies the use of different methods and different instruments to guarantee the quality of the optics and consequently of the delivered photons. In this work, we compare the performance of two "state of the art" instruments, aimed at the non-contact measuring of optical surface profiles. The first one is an in house modified version of the Long Trace Profiler (LTP) developed for grazing incidence optics by P.Z. Takacs and Al. The second is a Fizeau like interferometer (a WYKO RTI 4100), primarily used for 2D mapping of surfaces. The aim of this paper is to outline when, according to our experience, an instrument is preferable with respect to the other, what are the limits of both and what kind of improvement could be made. Some examples will be reported. Spatial frequency, calibration and systematic errors will be compared and outlined.
    Proceedings of SPIE - The International Society for Optical Engineering 08/2005; DOI:10.1117/12.618270 · 0.20 Impact Factor
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    ABSTRACT: A technique to probe defects buried inside extreme ultraviolet (EUV) masks has been implemented using a dark-field microscopy detection setup. Specific samples have been fabricated to evaluate the sensitivity of this technique. They consist of silicon oxide gratings of a few nanometers height, coated with 40 layer pairs of molybdenum-silicon. We observed images with a good contrast on samples with defects as low as 3 nm. However, the imaging mechanism of scanning dark-field microscopy is not linear and can produce image distortions. Conditions of correct imaging have been analyzed, and simulations have been performed that show good agreement with the experimental data. This work opens the way for a better understanding of the capability of at-wavelength inspection technique for EUV mask. (c) 2005 American Institute of Physics.
    Applied Physics Letters 07/2005; 87(2). DOI:10.1063/1.1984097 · 3.52 Impact Factor
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    ABSTRACT: The optical metrology laboratory of Elettra is equipped with some state of the art instruments for the characterization of high precision optical components for the UV and x-ray energy range. Among them, the most important is the Long Trace Profiler, which is capable of very accurate measurement of the shape of long aspheric mirrors. It is a direct slope measurement device, able to measure slope errors below the mrad level, once properly operated and calibrated. Our device is an LTP II model dating back to 1992. Nevertheless, it has been deeply in house modified during these years. Recently we have assembled a second optic head (OH) that could be used in spite of (or together with) the original one. This second OH works without folding mirrors and uses a set of short focal distance Fourier Transform lenses. The absence of folding mirrors reduces the source of systematic errors and the use of short focal distance lenses increases the angular acceptance of the instrument. This fact is particularly useful when short radius of curvature mirrors as well as high groove density variation gratings have to be measured. Some other modifications have been made to help the stitching procedure or to change the measurement set-up. These will be described in details.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2005; DOI:10.1117/12.618322 · 0.20 Impact Factor
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    ABSTRACT: A diffraction plane grating with single-layer coating able to reach photon energy up to 3 keV (possibly 4 keV) will be adopted at the TwinMic beamline at ELETTRA. The TwinMic beamline will exploit the unique capabilities of the novel twin X-ray microscope, which combines scanning and full-field imaging microscopes in a single multipurpose end-station. The needed moderate energy resolving power will be provided by a variable included angle plane grating monochromator working in a collimated light mode (also known as collimated SX700). This configuration allows freely selection of the incidence and diffraction angles at the grating, therefore permitting, for instance, to optimize its efficiency. This monochromator uses two mechanically ruled gratings to cover a very wide working energy range. The first grating goes from 150 eV to 1000 eV while the second goes from 600 eV to 4 keV. The two gratings were ruled using the CARL ZEISS Grating Ruling Engine GTM6, which is operated under interferometric control. The high-energy plane grating, with a line density of 600 lines/mm, has a triangular profile with a blaze angle of 0.4° and an apex angle of 178°. The grating profile is ruled on a silicon substrate and is covered with a 30 nm thick gold film. The small blaze angle permits one to work in blaze condition at very grazing incidence angles and therefore allows reaching high photon energies not accessible by means of conventional gratings.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2005; DOI:10.1117/12.619232 · 0.20 Impact Factor
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    ABSTRACT: Using photoemission spectromicroscopy at sub-micron lateral resolution we studied two superconductor systems of high fundamental and practical importance, such as Bi2Sr2CaCu2O{8+delta} and MgB2. Our findings demonstrate the importance of considering, for this class of Systems, the possible presence of spatial inhomogeneities in interpreting the results of conventional photoemission experiments, which typically probe an area of the order of 1 mm^2. In particular, in the case of MgB2, we report a measured density of states directly comparable to the theoretical predictions, thus rejecting the daim for the existence of strong correlation effects proposed by previous spatially averaged measurements.
    Journal de Physique IV (Proceedings) 03/2003; 104:487-490. · 0.35 Impact Factor
  • Journal de Physique IV (Proceedings) 01/2003; 104:487-490. DOI:10.1051/jp4:20030128 · 0.35 Impact Factor
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    ABSTRACT: The Long Trace Profiler (LTP) has proved to be one of the major metrological aids for the characterization of synchrotron radiation optics. Currently the optical components installed at the beamlines face higher and higher demands, requiring a precise calibration and control of the measuring conditions. One important parameter to be considered while scanning is the temperature drifts afflicting the measuring sessions. We will review our experiences about the influence of this parameter on the LTP ability in measuring very accurate optical surfaces. It is possible to discriminate at least four major sources of perturbations due to temperature changes: air turbulence, deformation in the optical train inside the LTP optics head, deformation of the optical surface under test (SUT) and deformation of the holders of the SUT itself. Some addresses on the curing of these perturbations can be obtained.
    International Symposium on Optical Science and Technology; 12/2002
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    ABSTRACT: Two bendable elliptical cylinder mirrors arranged in a Kirkpatrick-Baez (KB) geometry are installed at the Nanospectroscopy beamline at ELETTRA for refocusing soft x-rays provided by an APPLE II type undulator. This achromatic focusing device delivers the beam to a micrometer-scale, high photon density spot, which is the source for a Spectroscopic Photoemission and Low Energy Electron Microscope (SPELEEM). A similar second pair of KB mirrors will refocus the monochromated light in a second experimental station for a different imaging microscope. These four mirrors, developed by S.E.S.O., are manufactured from Glidcop™ in a U shaped design with 380mm length. They are electroless nickel plated for polishing and are bent into an elliptical shape applying two unequal end moments. They have been tested in the optical metrology laboratory of ELETTRA using an in-house modified version of the Long Trace Profiler (LTP): the surface slope variation as a function of the bender actuators has been measured to characterize the behavior of the bender mechanism and the accuracy of the elliptical profiles that can be achieved. Both metrological optical data and x-rays performances show the achievement of a microradian accuracy for the different profiles in which each mirror can be bent and the possibility to vary the focal distance by about 30-40% around the nominal value.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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    ABSTRACT: Using photoemission microscopy at submicron lateral resolution, we measured the occupied density of states in MgB2 single crystalline grains from commercial MgB2 powder. This experiment provided a reliable measurement of the integrated density of states in MgB2 directly comparable to the theoretical predictions. According to the conventional metallic nature of MgB2, with weak electron-electron correlation effects, we observe a close overall agreement between our photoemission valence-band spectrum and the calculated density of states. This is further supported by the analysis of the loss features in the B 1s photoemission spectrum. We also report evidence of a quick surface degradation due to the exposure to the synchrotron radiation beam.
    Physical Review B 10/2002; 66(13):-. DOI:10.1103/PhysRevB.66.132503 · 3.66 Impact Factor
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    ABSTRACT: An important application of photoemission spectromicroscopy would be to measure heterostructures and semiconductor devices in cross section to directly determine band offsets and band bending. We present here studies of p-n GaAs homojunctions and Al/GaAs Schottky junctions fabricated by molecular-beam epitaxy. Our results suggest that a minimum experimental uncertainty of about 0.15 eV will effect band offset determination. In general, useful quantitative information on the junction electrostatics can be obtained provided that the experimental data are analyzed to substract the diffuse photon background and take into account the intensity profile of the photon spot. © 2002 American Institute of Physics.
    Applied Physics Letters 04/2002; 80(14):2511-2513. DOI:10.1063/1.1468264 · 3.52 Impact Factor
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    ABSTRACT: A natural application of the emerging technique of photoemission microscopy to the study of semi-conductor interfaces involves measuring a device in cross section to directly determine heterojunc-tion parameters. We present here results on p–n GaAs homojunctions, which served as a prototype system to demonstrate the applicability of this technique to buried semiconductor interfaces. We also describe preliminary measurements of the electrostatic potential profile across Al/GaAs Schottky junctions.
    Surface Review and Letters 02/2002; 9(Vol. 9, No. 1):249-254. DOI:10.1142/S0218625X02002154 · 0.37 Impact Factor
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    ABSTRACT: The optics metrology laboratory of Sincrotrone Trieste is operating some non-contact interferometers since 1992, in order to characterise slope errors, figure deviations and surface roughness for synchrotron radiation optics (SR) up to 1.4 metres in length, prior to their installation at the beamlines. During these years, prompted by the increasing needs of experimentalists, the requirements for FEL and SR optical components have become more and more severe. We will review here the history of our measurements during the last nine years, comparing the match between the given specifications and measured optical quality of the delivered items. We will also illustrate which has been the evolution of the main optical concepts, that has ultimately boosted the suppliers to develop machining and testing methods to a novel level of accuracy.
    Proceedings of SPIE - The International Society for Optical Engineering 11/2001; DOI:10.1117/12.448490 · 0.20 Impact Factor