Abstract The European Electron Cyclotron Resonance Ion Source (ECRIS) community has more than 20 years of experience working together in various EU-funded projects. In the recent project, called ERIBS (European Research Infrastructure – Beam Services), the community will focus on improving ion beam services for the EURO-LABS (European-Laboratories for Accelerator Based Sciences) research infrastructures. The EURO-LABS is a four-year project funded by the Horizon Europe program of the European Commission for years 2022 - 2026. In the ERIBS collaboration the best expertise, know-how and practices of the ECRIS community will be exploited and transferred between the partners to take full advantage of the European ion source infrastructure. The aim is to extend the beam variety available for the European user community by developing beam production methods and techniques. This development includes further improvement of technologies related to high temperature ovens, axial sputtering and MIVOC method for all the participating laboratories. We will also aim to improve both short- and long-term plasma and beam stability, as well as methods for online monitoring of these conditions. This can be realized, for example, by optical emission spectroscopy, identifying kinetic plasma instabilities by means of hard x-ray detection and using online beam current monitoring systems. An example of the recent developments is the new collaboration proposed by the CNRS-IPHC team to synthesize enriched MIVOC compounds for the other ERIBS partners. For example, the team successfully prepared an enriched chromocene compounds, which were needed to produce intensive 54 Cr and 50 Cr beams for the JYFL and GANIL nuclear physics programs, respectively.
Single-atom transistors hold great promise for reducing semiconductor devices to their ultimate scale, approaching atomic dimensions. Typically these transistors use dopant atoms embedded in a semiconductor to form quantum-dot switches; unfortunately, in this approach shallow potential wells restrict device operation to cryogenic temperatures. This work extends the operation of single-atom transistors to $r\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}m$ $t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e$, by embedding dopant atoms in SiO${}_{2}$ tunnel barriers to form deep quantum wells. Nearby dopant atoms can communicate electrostatically, forming double quantum dots, opening a route toward practical, room-temperature atomic-scale quantum electronics.
Effect of strain on thresholdless Auger recombination processes in quantum wells has been studied theoretically. A detailed analysis of overlap integrals between the initial and final states of the particles has been carried out. It is shown that the strain both qualitatively and quantitatively affects the overlap integral between the electron and hole states. It is demonstrated that the Auger recombination rate decreases as compressive strain increases.
Using previously derived analytical expressions for the polarization field in nitride quantum dots (QDs), we show that the potential in the growth direction can be approximated as linear in such dots, and that the slope of this linear potential depends only on the aspect ratio (height/radius) of the dot. We demonstrate how the large polarization field leads to a linear dependence of the exciton energy on dot size, provided the aspect ratio of the dot is conserved while the size is varied. We also present a useful analytical approximation for the electron and hole wave functions in nitride QDs in terms of Airy functions, which compares well with the solutions of a numerical computation. We note that the disagreement concerning the sign of the shear piezoelectric coefficient ${e}_{15}$ leads to a significant uncertainty in the calculated potential.
We report on fabrication and transport properties of lithographically defined single quantum dots (QDs) in single electron transistors with ultrathin silicon-on-insulator (SOI) substrate. We observed comparatively large charging energy EC∼20 meV derived from the stability diagram at a temperature of 4.2 K. We also carried out three-dimensional calculations of the capacitance matrix and transport properties through the QD for the real structure geometry and found an excellent quantitative agreement with experiment of the calculated main parameters of stability diagram (charging energy, period of Coulomb oscillations, and asymmetry of the diamonds). The obtained results confirm fabrication of well-defined integrated QDs as designed with ultrathin SOI that makes it possible to achieve relatively large QD charging energies, which is useful for stable and high temperature operation of single electron devices.
Threshold characteristics of type II QW-lasers have been investigated theoretically. The rate of non-threshold channel of Auger recombination in type II heterostructures with quantum wells has been calculated. It is shown that the AR rate is a power function of temperature rather than an exponential one as in bulk materials. Feasibility of suppression of the Auger recombination process in the type II HS is demonstrated. The Auger current has a minimum and internal quantum efficiency has a maximum at a definite ratio of the barrier heights for electrons and holes. The possibility of controlling the AR current is shown to be very important for the creation of mid-infrared lasers operating at room temperature.
Fourier-transform infrared photoreflectance (PR) spectroscopy was used to study the energy spectrum of InSb/InAs/In(Ga,Al)As/GaAs metamorphic heterostructures with a superlattice waveguide at room temperature (RT). Theoretical calculations in the framework of the eight-band Kane model were performed to obtain a reliable knowledge of the actual energies of the most probable optical transitions. The experimental results were analyzed to determine the influence of the design features and stress balance on the energy spectra of the structures. Photoluminescence studies performed at 11 K and RT, as well as the determination of the internal quantum efficiency of luminescence, enabled us to characterize the emission characteristics of the structures, regardless of their waveguide efficiency. The structure with a 5-nm-thick GaAs insertion within the metamorphic buffer layer exhibited the highest probability of the main optical transition observed in the PR spectra as well as the highest luminescence intensity and quantum efficiency.
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