| 1. |
- Vomiero, Alberto, et al.
(författare)
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Structural properties of reactively sputtered W-Si-N thin films
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102:3
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten-silicon-nitrogen, W-Si-N, ternary thin films have been reactively sputter deposited from W5 Si3 and W Si2 targets using several nitrogen partial pressures. The films have been thermal annealed in the 600-1000 °C temperature range and a wide region of the W-Si-N ternary phase diagram has been explored by changing the N2 Ar ratio during the deposition. Multitechnique approach was adopted for the analysis of the samples. Composition has been determined via ion beam analysis; chemical states were investigated using x-ray photoelectron spectroscopy (XPS); crystalline structure was studied using transmission electron microscopy (TEM) and x-ray diffraction (XRD) and surface morphology by scanning electron microscope. The films deposited in pure argon atmosphere are tungsten rich and approach the target contents as N2 Ar ratio is varied during deposition. Tungsten enrichment in the films is caused by resputtering of silicon which can be inhibited by the formation of silicon nitride, allowing films with SiW ratio closer to the target compositions. The higher capability to form nitrides with silicon than with tungsten favors enhancement of nitrogen content in samples deposited from the silicon rich target (W Si2). The samples with excess nitrogen content have shown losses of this element after thermal treatment. XPS measurements show a break of W-N bonds caused by thermal instability of tungsten nitrides. TEM and XRD revealed the segregation of tungsten in form of metallic or silicide nanoclusters in samples with low nitrogen content (W58 Si21 N21 and W24 Si42 N34). High amounts of nitrogen were revealed to be highly effective in inhibiting metallic cluster coalescence. Measurements of electrical resistivity of as deposited films were performed using four point probe technique. They were found to lie in the range between 0.4 and 79 m cm depending on sample composition. © 2007 American Institute of Physics.
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| 2. |
- Carturan, S., et al.
(författare)
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Formation of silver nanoclusters in transparent polyimides by Ag-K ion-exchange process
- 2007
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 42:2, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoclusters embedded in two transparent fluorinated polyimides, 4,4'-hexafluoroisopropylidene diphthalic anhydride - 2,3,5,6-tetramethyl paraphenylene diamine (6FDA-DAD) and 3,3',4,4' - biphenyltetracarboxylic acid dianhydride - 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (BPDA-3F), have been produced by surface modification with KOH aqueous solution followed by K-assisted Ag doping and thermal reduction in hydrogen atmosphere. The reaction rate of the nucleophilic hydrolysis in KOH, studied by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectrometry (RBS), depends on the polyimide chemical structure. After ion-exchange in AgNO 3 solution and subsequent annealing, the polyimide structure recovery was monitored by FT-IR whereas the characteristic surface plasmon absorption band of silver nanoparticles was evidenced by optical absorption measurements. The structure of silver nanoclusters as related to size and size distribution in the different polyimide matrices was thoroughly investigated by Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The collected data evidenced a uniform distribution of Ag clusters of nanometric size after thermal treatment at 300 °C in both polyimides. For the same ion-exchange treatment parameters and annealing temperature, XRD analyses evidenced the presence of crystallites with similar sizes. © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.
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| 3. |
- Afanasiev, Sergey V., et al.
(författare)
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Experimental apparatus to study crystal channeling in an external SPS beamline
- 2007
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6634
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Tidskriftsartikel (refereegranskat)abstract
- For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets.1 We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 μrad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass efficiency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.
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| 4. |
- Baricordi, S., et al.
(författare)
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Optimal crystal surface for efficient channeling in the new generation of hadron machines
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:6
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Tidskriftsartikel (refereegranskat)abstract
- The new generation of hadron machines may profitably take advantage of channeling for steering and collimation of high-energy particle beams. In that case, the requirements on the quality of the crystal surface are rather stringent in terms of both lattice perfection and roughness. Here, the authors show the structural and morphological characterizations of crystals fabricated through a method to achieve a surface that fulfills all needed specifications for application in hadron machines. © 2007 American Institute of Physics.
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