A. Bianco

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

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Publications (25)31.47 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.
    Proc SPIE 05/2011;
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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 01/2011; 635(1). · 1.14 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. · 2.19 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: 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: 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 01/2009; 606(3):780-784. · 1.14 Impact Factor
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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: 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. © 2005 American Institute of Physics. Inspection of defects in mask blanks for the extreme ultraviolet EUV lithography is of a great importance for the progress of this technology in the microelectronic industry. EUV masks are patterned Bragg mirrors that reflect light at a 13.5 nm wavelength. They are made of a stack of 40 pairs of molybdenum/silicon Mo/ Si on a glass substrate. The pres-ence of particles during the deposition step will disturb the structure of the multilayer, and may create a local bump at the top of the Bragg mirror. 1 The response of the reflected radiation to a localized perturbation results in a loss of inten-sity in the aerial image, thus potentially creating an un-wanted pattern in the resist. 2 Very stringent requirements have to be met in terms of the number and size of defects. The specifications required by the International Technology Roadmap for Semiconductors is fixed to a maximum density of 1 10 −2 defects/ cm 2 of less than 50 nm in diameter. 3 Dedicated metrology equipment able to detect such defects have to be developed. Inspection using deep ultraviolet light at a wavelength of 257 nm is used in the mask manufactur-ing industry. This provides a contrasted image of the ab-sorber patterns and defects present on top of the mask blank, 4 but this technique is not able to probe the multilayer and image buried defects. 5 Methods based on at-wavelength in-spection have already been implemented, and have shown the high potential of this technique. The comparison between at-wavelength bright-field and dark-field measurements shows the advantages and the limits of these two types of techniques. Dark-field microscopy seems to be the best can-didate in that it gives good results in terms of sensitivity. Two types of setups have been already implemented. Using scanning dark-field microscopy, detection of phase defects as small as 60 nm in width and 3 nm in height has been already reported. 6,7 More recently full-field imaging in dark-field mode has demonstrated its capability to provide good spatial resolution detection of a buried defect of 70 nm in width and 2 nm in height. 8 We have recently confirmed the poten-tial of the dark-field scanning microscopy to detect shallow buried defects. 9 However, the main focus of the present letter is to point out and clarify the specific imaging mechanism associated with this technique. To perform dark-field inspection in the EUV range, we used the Spectromicroscopy beamline at the Elettra Synchro-tron Radiation Facility in Trieste, Italy. 10 This beamline uses a photon energy of 95 eV—corresponding to a wavelength of 13.1 nm—and is ended by a Schwarzschild objective which produces an EUV spot of 0.5 m full width at half maximum. The acquisition of the image is performed by scanning the sample under the spot. The principle of dark-field microscopy consists of the measurement of the light diffracted and scattered by the defects, and detected in the dark cone of the Schwarzschild objective by the photodiode Fig. 1. In order to study the mechanism involved in the image formation, dedicated samples of multilayer buried de-fects were realized. These microstructures consist of gratings of silicon oxide with depths ranging from 3 nm to 22 nm, manufactured by wet etching. The grating period ranges
    Applied Physics Letters 01/2005; · 3.79 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 - J PHYS IV. 01/2003; 104:487-490.
  • Journal de Physique IV (Proceedings) 01/2003; 104:487-490. · 0.29 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. · 3.79 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 01/2002; 9(Vol. 9, No. 1):249-254. · 0.28 Impact Factor
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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 01/2002; 66:-. · 3.77 Impact Factor
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    ABSTRACT: In the course of 1998, the Spectromicroscopy beamline at ELETTRA completed commissioning and succeeded in performing its first test experiments. The beamline is designed to perform photoemission experiments with high spatial resolution, which is obtained by focusing the radiation in a small spot on the sample by means of a multilayer-coated Schwarzschild Objective. Three objectives are currently available; these operate at photon energies of 74, 95, and 110 eV. A review is presented of the performances achieved together with an outlook on the future upgrades of the microscope. The smallest achievable spot size is currently 0.5 mu m. At present, the limit to the spatial resolution is due to aberrations caused by figure errors of the objective. Typical counting rates in photoemission spectra, for example, on the Au 5d peak, are of the order of 10(4)-10(5) counts per second with an energy resolution of the order of 100-200 meV. Among the first experiments in which p- and n-type GaAs layers of 0.25 mu m thickness were imaged. (C) 2000 American Institute of Physics. [S0034-6748(00)04001-6].
    Review of Scientific Instruments 01/2000; · 1.60 Impact Factor
  • Proc SPIE 01/1997;
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    ABSTRACT: In the past few years a number of variable angle spherical grating monochromators (VASGM) have been proposed and installed at Elettra beamlines. At present one of them (ESCAmicroscopy beamline) is operating, two (Spectromicroscopy and GasPhase photoemission beamline) are under commissioning, and one (Circulary Polarized Light beamline) is under construction. Although the experimental requirements of these monochromators are different, their control principles are the same. Approximately one year ago we started a project that aimed to provide a uniform and adequate system for controlling these monochromators. The paper deals with several frameworks of this project. First the monochromator software architecture is explained whereby the monochromator high level application options are explained. Instead of using extensive look up tables for the relationship between the energy and the angles of the mirror and gratings, we tried to develop an on-line mathematical model for energy tuning. An interesting feature of this model is that all monochromator data are parametrized which is important for the monochromator calibration. Much effort has been spent in order to understand the drive unit positioning behavior in the submicron scale which is non linear as a function of motor steps. As a result of this study some common drive unit mechanical properties were fixed according to which an absolute drive unit positioning control software is proposed. Finally we discuss some topics regarding the monochromator calibration and resolution optimization.
    01/1997: pages 76-85;
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    ABSTRACT: High brightness, third‐generation synchrotrons allow diffraction‐limited performance and large flux for scanning photoemission microscopes. A new microscope, SuperMAXIMUM, is being developed at the University of Wisconsin Center for X ray Lithography in collaboration with the Sincrotrone Trieste. The beamline, being built in Trieste, uses a variable angle spherical grating monochromator (VASGM). A combination of rotation of a plane mirror and rotation of the spherical grating keeps the slit positions and beam directions fixed. The microscope objectives are normal‐incidence, multilayer‐coated Schwarzschild objectives. The project, which is nearing completion, utilizes novel designs for optics alignment, sample rastering mechanics, and software control. We will discuss the project status, new designs, and techniques. © 1996 American Institute of Physics.
    Review of Scientific Instruments 10/1996; · 1.60 Impact Factor
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    ABSTRACT: Using (secondary) photoelectron emission microscopy, we studied the fully formed 80 Å Pt/n–GaP(001) interface with a lateral resolution better than 2 μm. We probed the chemically etched and sulfur passivated GaP(001) surface by ultraviolet and soft x rays. The radiation source was either a deuterium lamp or the radiation from ELETTRA’s U12.5 undulator. Due to their escape depth, the photoemitted secondary electrons carry chemical information of buried interfaces. The use of tunable synchrotron radiation enabled us to obtain chemical contrast by digital subtraction of the microimages taken at photon energies above and below each core‐level absorption edge. The microimages revealed lateral changes in photoyield efficiency and chemical composition. The results were confirmed by x‐ray photoemission spectromicroscopy measurements performed using Al Kα radiation. © 1996 American Institute of Physics.
    Journal of Applied Physics 09/1996; · 2.21 Impact Factor
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    ABSTRACT: We studied the Ptn-GaP buried Schottky junction by several spatially resolved techniques to correlate the chemical inhomogeneities of the interface with the spatial variations of the diode transport properties. The recombination rate fluctuations and small spatial variations (3–8 meV) of the Schottky barrier height were correlated with the local stoichiometry of the bare GaP surface and of the fully formed junction. We discovered regions with local segregation of metallic gallium. In these regions we measured a Schottky barrier height only 4 meV lower than in the stoichiometric areas. On the contrary these zones presented a more important electron-hole recombination rate.
    Applied Surface Science 01/1996; 104:196-203. · 2.11 Impact Factor
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    ABSTRACT: The concept of variation of the angle of deflection in a spherical grating monochromator allows to keep the defocus aberration at zero while keeping the entrance and the exit slit distances fixed. This report presents the optimization of this concept for different applications in which one would always like to work with maximum resolving power and photon flux while keeping the exit slit at a fixed position. Three designs are presented for medium resolution (E/ΔE = 3000) soft x‐ray microscopy studies in the photon energy range 200–1200 eV and 20–300 eV and for high‐resolution spectroscopy (E/ΔE≳10 000) in the larger range 20–800 eV. © 1995 American Institute of Physics.
    Review of Scientific Instruments 03/1995; · 1.60 Impact Factor