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our research
Phys. Rev. Materials 3, 023001(R) (2019)
Segregation scheme of indium in AlGaInAs nanowire shells
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Quaternary alloys enable the independent optimization of different semiconductor properties, such as the separate tuning of the band gap and the lattice constant. Nanowire core-shell structures should allow a larger range of compositional tuning as strain can be accommodated in a more effective manner than in thin films. Still, the faceted structure of the nanowire may lead to local segregation effects. Here, we explore the incorporation of indium in AlGaAs shells up to 25%. In particular, we show the effect of In incorporation on the energy shift of the AlGaInAs single-photon emitters present in the shell. We observe a redshift up to 300 meV as a function of the group-III site fraction of In. We correlate the shift with segregation at the nanoscale. We find evidence of the segregation of the group-III elements at different positions in the nanowire, not observed before. We propose a model that takes into account the strain distribution in the nanowire shell and the adatom diffusion on the nanowire facets to explain the observations. This work provides novel insights on the segregation phenomena necessary to engineer the composition of multidinary alloys.
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our research
Solid State Ionics 330, 17 (2019)
Nano-scale oxide formation inside electrochemically-formed Pt blisters at a solid electrolyte interface
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We report on platinum oxide formation during electrochemical anodic polarization of a platinum film on yttria-stabilized zirconia (YSZ) under electrochemical oxygen potential control. The electrochemical potential drives oxygen through the YSZ electrolyte towards a nominally 175 nm thin Pt film, which we found to locally delaminate from the substrate by forming nano-scale blisters. High resolution scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) mapping of focused-ion beam (FIB)-prepared cross-sections of single bubbles of a few micrometers in diameter reveal them to be hollow and enclosed by a Pt outer and a few tens of nanometers thick PtOx inner shell. The oxide shell presumably formed due to the increase of local oxygen chemical activity under the applied process conditions (723 K, 500 mbar O2, bias voltage +100 mV). Interface X-ray diffraction indicates that the solid electrolyte surface morphology is largely unaffected by the process suggesting that the YSZ surface is stable on the atomic scale under application relevant oxygen transport conditions. Platinum is known to be rather stable towards oxidation, even at elevated oxygen pressure, leading to oxide-scale thicknesses of the order of 1 nm. Our results however indicate that many of the kinetic barriers for oxidation during the nano-confined blistering process are lowered. This may have implications in general for the mechanism how oxygen is stored in an electrode at such an internal metal - oxide/metal - gas interface, which is important for the functionality of many solid-state electrochemical and memresistive devices.
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from our users
Scientific Reports 8, 18054 (2018)
GeVn complexes for silicon-based room-temperature single-atom nanoelectronics
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We propose germanium-vacancy complexes (GeVn) as a viable ingredient to exploit single-atom quantum effects in silicon devices at room temperature. Our predictions, motivated by the high controllability of the location of the defect via accurate single-atom implantation techniques, are based on ab-initio Density Functional Theory calculations within a parameterfree screened-dependent hybrid functional scheme, suitable to provide reliable bandstructure energies and defect-state wavefunctions. The resulting defect-related excited states, at variance with those arising from conventional dopants such as phosphorous, turn out to be deep enough to ensure device operation up to room temperature and exhibit a far more localized wavefunction.
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Deliverables view all
WP7 - JRA2 - Research on High Precision Manufacturing
D7.15 - Realization of coplanar electrode arrays with 10 nm gaps
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There is growing interest in the study of the electrical properties of single nano-objects. This deliverable demonstrates the successful fabrication of arrays of nanogaps via exploiting the precision of growth processes for lateral patterning, as the nanogaps arrays could be used as a substrate to correlate the structural properties of nanomaterials immobilized between the gaps with their electrical properties. In particular, technologies for fabrication of metallic nanogaps down to 10 nm and nanogaps arrays, as well as arrays of individual nanogaps, have been developed. Also fabrication parameters have been optimized for minimising leakage currents and improving electrode characteristics. Current technology is now readilly available for the needs of NFFA users via the transnational access procedure.
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WP10 - JRA5 – Nano-Object Transfer and Positioning
D10.6 - Test experiment of transfer and positioning system to a soft X-ray microscopy setup
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This JRA5 deliverable report D10.6 “Test experiment of transfer and positioning system to a soft Xray microscopy setup” describes the status of the implementation of the transfer and positioning system to the soft X-ray microscopy setups at SOLEIL, France. All technical prerequisites have been developed, are readily available for use and are in particular as part already offered to NFFA transnational access users. In particular, both, the nano-transfer tool developed within JRA5, including the three columns i) the Matlab and Python implementation of the software script, ii) the “hierarchical marker design on demand” as well as iii) the electron- (EBID) and ion-(IBID) induced deposition, as well as the capabilities for a nano-transfer at the SOLEIL beamlines are all implemented and integrated. The goals of all three columns have been achieved, as separately documented in several JRA5 deliverable reports. The software-setup and the marker technology has been tested and approved, and are ready to use. At the soft X-ray beamlines at SOLEIL dedicated for the “Advanced Nano- Object Transfer and Positioning” the equipment and technical infrastructure ensures compatibility and easy implementation. In a test experiment to be scheduled at the time of the deadline, the full integration of the nanotransfer tool on one hand and the positioning devices at the SOLEIL beamline at the other hand will be shown. At the same time, the array markers created by direct-write non-linear lithography at FORTH will be utilised to permit a nano-transfer based on the re-location of selected nano-objects at a nano-science centre to a soft-X-ray beamline setup at an Analytical Large Scale Facility (ALSF). We in particular stress here that the compatibility between the modular transfer and positioning system and the hardware at the two dedicated SOLEIL parallel imaging X-ray photoemission electron microscope (XPEEM) and the scanning microscope (STXM) beamlines at SOLEIL has been achieved and the technical feasibility of D10.6 is assured.
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WP11 - NA – Innovation and networking activities
D11.15 - Third Annual report on NFFA-EUROPE dissemination activities
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The dissemination and awareness activities of NFFA-Europe heavily contributed to the success of the NFFA-Europe project. Its very positive impact to the TransNational Access programme, this is shown by the large number of proposals submitted for the use of the NFFA-Europe infrastructure. During the third year, the activities were not only kept at the same level of the previous years but were broadened, because the end of the project is still far away and there is atill enough time to approach new users for let them use the infrastructure available within the NFFA-Europe project. During the third year the NFFA-Europe project has been presented at 22 conferences; two dedicated NFFA-Europe events have been organized; two issues of the NFFA-Europe Newsletter have been published and distributed to a number of scientists; an advertisment page has been published reaching a huge number of scientists. The international collaborations to US and Australian similar projects are producing good results in terms of future collaborations. The NFFA-Europe dissemination programme is definitely in line with the expectations.
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Transnational Access Statistics
11 calls for access
355 proposals submitted
65% rate of acceptance
32% with Large Scale Facilities
13% with theory
10% with industry
~3 average users per proposal
43 countries applying
1076 lab sessions