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JSR, Volume 31, Part 6 (2024)
Development of hard X-ray photoelectron spectroscopy in liquid cells using optimized microfabricated silicon nitride membranes
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We present first hard X-ray photoelectron spectroscopy (HAXPES) results of aqueous salt solutions and dispersions of gold nanoparticles in liquid cells equipped with specially designed microfabricated thin silicon nitride membranes, with thickness in the 15–25 nm range, mounted in a high-vacuum-compatible environment. The experiments have been performed at the HAXPES endstation of the GALAXIES beamline at the SOLEIL synchrotron radiation facility. The low-stress membranes are fabricated from 100 mm silicon wafers using standard lithography techniques. Platinum alignment marks are added to the chips hosting the membranes to facilitate the positioning of the X-ray beam on the membrane by detecting the corresponding photoemission lines. Two types of liquid cells have been used, a static one built on an Omicron-type sample holder with the liquid confined in the cell container, and a circulating liquid cell, in which the liquid can flow in order to mitigate the effects due to beam damage. We demonstrate that the membranes are mechanically robust and able to withstand 1 bar pressure difference between the liquid inside the cell and vacuum, and the intense synchrotron radiation beam during data acquisition. This opens up new opportunities for spectroscopic studies of liquids.
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ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY – Volume 27, issue 2, page 229-240
Microstructure of VO2 Thin Films Synthesized by Pulsed Laser Deposition
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In this paper, pulsed laser deposition (PLD) at low partial oxygen pressure(similar to 10 mTorr) was used to obtain VO2 thin films. During the PLD, the deposition temperature and number of pulses were varied in order to obtain a good sample crystallinity. It was showed by atomic force microscopy(AFM) micrographs that the mean grain size increasedfrom similar to 40 nm to similar to 90 nm at a variation of the deposition temperature from 400(degrees)C to 500(degrees)C.Further, by increasing of both substrate temperature and number of pulses, the mean grainsize increases to 220 nm. According to the Rietveld refinement of the experimental X-ray diffraction(XRD) pattern, within the grain size increasing, the mean crystallite size increased from 14 nm to 22 nm, as well as a decreasing of the lattice strain from 0.29% to 0.20%.These dependencies further imply a decreasing of the dislocation density of 2.3 to0.9x10(12)cm(-2). At the same time, the optical band gap decreased from 0.72 eV (400(degrees)C) to0.66 eV (500(degrees)C), reaching 0.60 eV (600(degrees)C). Further investigations performed by X-ray photoelectron spectroscopy(XPS) showed the vanadium oxide presence, by the spin-orbit splitting of approximately 7.5 eV betweenV2(p3/2)andV2(p1/2)orbitals. Finally, the electrical measurements done in the range of 250-370K reveal a close relationship between the dislocation density and the observed resistance-temperature dependence.
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Small 2024, 2405411
On-Chip Thermoelectric Devices Based on Standard Silicon Processing
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The strong reduction of thermal conductivity with respect to bulk silicon makes nanostructured silicon one of the best materials for highly efficient direct conversion of heat into electrical power and vice-versa. The widespread technologies for the integration of silicon devices can be used to define on-chip micro thermoelectric generators (scavengers); similar structures could also be used for precise and well-localized cooling through the reverse process of heat pumping. However, the road to the fabrication of integrated thermal energy scavengers or cooler, based on silicon, is still very long. In this work, the design and the fabrication process of on-chip thermoelectric devices based on a large number of interconnected monocrystalline silicon nanobeams, very tall (>1 µm) and thin (less than 200 nanometers), arranged in large areas combs is shown. The small width of the nanobeams gives a reduced thermal conductivity, and the height perpendicular to the substrate allows the definition of a highly dense collection of nanostructures. The total cross-section is far broader than that of other nanostructures, a characteristic that guarantees both mechanical stability and larger deliverable power per unit area.
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Deliverables view all
WP11 - JA1 - Real-time observation and control in microscopy and spectroscopy of nano-objects
D11.7 - Implementation of STM microscopy for investigation of solid/liquid interfaces under welldefined gas atmospheres and with electrochemical control (EC-STM)
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Investigating materials and processes in realistic environments is crucial for understanding and designing materials for applications in energy storage, catalysis, corrosion resistance, and nanotechnology. In this context, one of the key objectives of JA1 is to integrate operando capabilities into scanning tunneling microscopy (STM) experiments in multiphase environments. Specifically, sub-task 11.1.2 focuses on setting up versatile electrochemical STM (EC-STM) systems and developing user-friendly protocols for in-situ electrochemical STM, enabling operation at solid/liquid interfaces under well-defined gas atmospheres and with electrochemical control. To this end, two custom-built EC-STM systems have been set up that are based on the same platform developed by the Wandelt research group (Uni Bonn) that is characterized by a rugged design, great flexibility concerning various electro-chemical environments, and excellent performance regarding lateral spatial resolution [1]. While the system at ICN2 has been developed to offer optimized, user-friendly protocols for external users and will complement the advanced characterization tools available at ICN2 through the NFFA, the reference system at TUM has been optimized to host high-speed capabilities, enabling operando experiments on electrochemically relevant systems with sub-s time resolution. Given TUM's extensive technical and research experience in electrochemical STM, and the fact that both systems share the same design, the transfer of knowledge in nearly all technical aspects has been crucial for the successful implementation of the ICN2 system.
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WP12 - JA2 - X-ray Wavefront Metrology, Correction and Manipulation
D12.5 - User Experiment with OAM beam
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Electromagnetic waves with orbital angular momentum (OAM) are increasingly used in optical communications, quantum technologies, and optical tweezers. Recently, they have shown potential for detecting helical dichroic effects in chiral molecules and magnetic nanostructures. In this study, we used single-shot ptychography on a nanostructure with extreme ultraviolet OAM beams of varying topological charge (ℓ) at a free-electron laser. By adjusting ℓ, we improved image resolution by 30% compared to standard Gaussian beams, advancing coherent diffraction imaging and enabling sub-100 nm time-resolved microscopy over large sample areas.
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WP13 - JA3 Nano-engineering and pattern transfer methods
D13.4 - Library of processes based on advanced nano-engineering for TA
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In the current document we report on a selection of new processes developed within the NFFA (NEP) project related to advanced nanoengineering for transnational access (TA). They form a new library of process steps enabling new or improved capabilities for some specific nanopatterning. They are complementary and generally compatible with state-of-the-art microelectronics industry. Besides developing the individual core technology, we paid particular attention to novel groupings in a mix-and-match approach to study possible combinations of processes to maximize enabling capabilities for nanosystems manufacturing.
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Transnational Access Statistics
28 calls for access
970 proposals submitted
63% rate of acceptance
29% with Large Scale Facilities
12% with theory
11% with industry
~3 average users per proposal
65 countries applying
2949 lab sessions