Добірка наукової літератури з теми "Ge-2H"

Tolerance to boron (B) toxicity in barley (Hordeum vulgare L.) is partially attributable to HvNIP2;1, an aquaporin with permeability to B, as well as to silicon, arsenic and germanium (Ge). In this study, we mapped leaf symptoms of Ge toxicity in a doubled-haploid barley population (Clipper × Sahara 3771). Two quantitative trait loci (QTL) associated with Ge toxicity symptoms were identified, located on Chromosomes 6H and 2H. These QTL co-located with two of four B toxicity tolerance loci previously mapped in the same population. The B toxicity tolerance gene underlying the 6H locus encodes HvNIP2;1, whereas the gene(s) and mechanisms underlying the 2H locus are as yet unknown. We provide examples of the application of Ge in studying specific aspects of B toxicity tolerance in plants, including screening of wheat (Triticum aestivum L.) and barley populations for altered function of HvNIP2;1 and related proteins. In particular, Ge may facilitate elucidation of the mechanism and gene(s) underlying the barley Chromosome 2H B tolerance locus.

The two excited 0+ states of the neutron-rich nuclei 82 Ge , 84 Se and 86 Kr are explained as 2-particle 2-hole (2p–2h) excited states associated with two different open-shells of Z = 28–50 and 28–40. Also, a configuration of 1p–1h 7+ state is assigned to the 3689 keV state in 82 Ge . These 1p–1h and 2p–2h excitation energies support the decreasing of the N = 50 shell gap when Z changes from 40 to 32. A N = 50 shell gap of 3.67 MeV for 78 Ni is extracted from an extrapolation of the known data.

Silicon and Germanium crystallize in the cubic diamond structure 3C with which they dominate definitely the electronics. Playing on crystal phases in semiconductors occurs to be a valuable mean of electronic band engineering. Remarkably, the hexagonal 2H phase of SiGe turns to get a direct band gap with light emission capabilities within a specific composition range (Si<35%). This material holds the promise to fill the gap between electronics and photonics industry using group IV semiconductors. We use GaAs NWs with the wurtzite structure as a template to create both (1) core/shell and (2) trunk/nanobranches heterostructures [2,3]. The GaAs-wurtzite is an ideal template to copy the structure by epitaxy forcing the Ge to adopt the hexagonal crystal phase and in turn it is used here as a textbook case The growths are followed using the in situ TEM NANOMAX. This unique microscope can be implemented either with molecular beam epitaxy (MBE) sources or with a gas injector for chemical vapor deposition (CVD). Real time TEM observations at the atomic scale show the fundamental aspects of the epitaxy and the formation of growth-related staking faults in Ge-2H. 1) On core/shell configuration[1], depending on growth conditions, different growth regimes highly impact the crystal quality of the of Ge-2H shell. On {1-100} prismatic surfaces, a regular step flow supports a flat surface and a perfect replication of the hexagonal structure However, when the step flow is destabilized, original intrinsic I3 basal stacking faults (BSF) are formed during growth. We evidence their correlation with the growth modes related to surface diffusion. Understanding the nucleation of these defects is necessary to prevent their formation during epitaxy. Possible scenarios of I3 BSF formation are discussed. Theses defects show a faulted stacking ABACABAB with only one faulted basal plane bounded by a pair of partial dislocations along <11-20> with opposite Burger vectors b=+/-1/3<1-100>. Thermal annealing induces a motion of the dislocation and an expansion of the I3 BSF resulting in a 4H stacking in the core/shell structure. 2) On wurtzite GaAs nanowires, Au catalysts are deposited on the sidewalls. Nanobranches grow with an axial direction along <1-100> and exhibit a hexagonal crystal structure[2] . With in situ observations, we study the VLS and VSS growths of Au catalyzed Ge-2H branches depending on the growth temperature. [1] L. Vincent et al. Adv. Mat. Inter. 9-16 (2022) 2102340, doi.org/10.1002/admi.202102340 [2] A Li et al. Nanotechnology 34 (2023) 015601 doi: 10.1088/1361-6528/ac9317 Figure 1

To improve the quality of AlN layer deposit on SiC/Si, different Ge amounts (0.25, 0.5, 1, 2ML) were deposited before the carbonization process at the silicon substrate in order to reduce the lattice parameters mismatch between Si and SiC grown layers. The residual stress of the hexagonal AlN layers derives from the phonon frequency shifts of the E1(TO) phonon mode. The crystalline quality of the AlN layer is correlated to and investigated by the full width of the half maximum (FWHM) and the intensity of E1(TO) mode of the 2H-AlN. Best crystalline quality and lower stress value are found in the case where 1ML of Ge amount is predeposited. The E1(TO) mode phonon frequency shifts-down by 3 cm-1/GPa with respect to an unstrained layer.

Cross section measurements of neutron induced reactions on isotopes of Ge and Hf have been determined at energies 8.8, 9.6, 10.6, 11.1, 11.4 MeV using the activation technique. Neutrons produced by the 2H(d,n)3He reaction were used to irradiate pellets of natural Ge and Hf02- The neutron flux at the target position was determined using the 27Al(n,a)24Na, 93Nb(n,2n)92mNb and 197Au(n,2n)196Au reference reactions. HPGe detectors of relative efficiency εΓ=80% and 55% were used to determine the decay of the produced unstable nuclei. The cross section values were compared with those taken from the literature.

Ge precipitates in Al are known to form in a rich variety of shapes and orientation relationships. In this work it is shown that initial non-equilibrium shapes such as plates, laths, needles and tetrahedra can be induced to change to the equilibrium shape of an octahedron by proper temperature cycling. Analysis of this effect in bulk samples was complemented by direct observations of its mechanisms during in-situ temperature cycling.A bulk sample of an Al-1.8at%Ge alloy was solid solution annealed at 420°C for 2h, quenched in ice water, pre-aged at room temperature for 72h and then annealed for 5h at 250°C. Subsequently, part of the sample was repeatedly cycled between 250°C and 360°C. TEM specimens were prepared from both the cycled and non-cycled bulk sample by conventional electropolishing and examined in a JEOL 200CX electron microscope. The in-situ temperature cycling was carried out in a Kratos 1.5 MeV HVEM equipped with a double tilt heating stage.

ABSTRACTObjectives:Practical methods to determine gastric emptying (GE) and small intestinal transit time in preterm infants are required. The aim of this study was to develop a scintigraphic method to determine GE and small intestinal transit time in preterm infants which produce minimal radiation exposure and physical disturbance in these infants.Methods:Ten premature infants were studied. Median (and range) for gestational age was 28.9 (26–33) weeks, postnatal age was 19 (6–37) days, birth weight was 1194 (687–2300) grams and feeding volume was 173 (6–205) mL/kg/day. Nine of the patients were on nasal continuous positive airway pressure; one patient was on mechanical ventilation. A dose (0.2–0.4 MBq) of 99mTc‐DTPA (0.5 mL) was given at the end of a meal administered by naso‐gastric tube. Static images were obtained with a mobile gamma camera during the next 9 to 12 hours. The radiation dose was at most 0.30 mSv. Regions of interest (ROIs) were drawn around the stomach and the cecum. Time‐activity curves were generated. Gastric emptying half‐time (T½GE) was calculated. Residual gastric activity after 1 hour (R (1h)) and after 2 hours (R (2h)) was determined. Orocecal transit time was defined as the time until significant increase in activity was detected in the cecal ROI.Results:Images showed gastric emptying in all cases. Median (range) half time was 1.0 (0.5–3.0) h. R (1h) was 37.5% (19% to 100%), R (2h) was 23% (6% to 61%). In one patient the tracer did not reach the cecum within 12 hours. In the remaining nine patients orocecal transit time was 3.1 (1.3–6.1) h.Conclusions:We present a new scintigraphic method to determine GE and orocecal transit time. It appears safe and practicable as a research tool in preterm infants.

Single crystals of the intercalation compounds Ge1/3NbS2 andGe1/4NbS2 have been prepared by heating of the elements at 1073 K and by chemical transport with iodine at 923 to 1073 K. Their crystal structures were determined by single crystal X-ray methods.Ge1/3NbS2 (P63/mcm, a=5.767(1), c=13.518(3) Å, Z = 6) crystallizes with a superstructureof 2H-NbS2, characterized by layers of edge-sharing NbS6 trigonal prisms. The Ge atoms in the octahedral voids of the van der Waals gap are sixfold coordinated by sulfur. The NbS2-sublattice of Ge1/4NbS2 (P63/mmc, a = 3.339(1), c = 37.326(7) Å , Z = 6) represents a new 6H-polymorph. Herein, the Ge atoms are located either in the centers of the octahedral voids (c. n. = 6) or shifted from this position along [001] (c. n. = 3 + 3). The unusual electronic state and the bonding situation of germanium in the van der Waal gaps of NbS2 and the metal-metal bonding are studied in detail by using DFT band structure calculations.

Τhe 70Ge(n,2n)69Ge, 72Ge(n,a)69mZn, 72Ge(n,p)72Ga and 73Ge(n,p)73Ga reactions have been measured by means of the activation technique at neutron energy 17.9 MeV. The quasimonoenergetic neutron beam was produced via the 2H(d,n)3He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR “Demokritos.” Isotopically highly enriched targets of 70Ge, 72Ge and 73Ge, provided by the nTOF collaboration at CERN, have been used, thus allowing accurate cross section measurements since no corrections are needed to compensate for the parasitic reactions from neighboring isotopes that exist in the case of using natural Ge target. The cross section has been deduced with respect to the 27Al(n,α)24Na reference reaction.

Le silicium et le germanium, qui cristallisent dans la structure cubique du diamant (notée 3C), ont été les piliers de l'industrie électronique grâce à leurs propriétés intrinsèques. Néanmoins, l'ingénierie des phases cristallines métastables a émergé comme une méthode puissante pour ajuster les structures de bande électronique, ouvrant la voie à de nouvelles fonctionnalités tout en maintenant une compatibilité chimique. Notamment, le Ge dans la phase hexagonale 2H présente un gap direct de 0,38 eV. L'alliage SixGe(1-x)-2H présente une émission lumineuse intense avec une longueur d'onde modulable entre 1,8 µm et 3,5 µm, selon la concentration en silicium (40 % à 0 %). Ces propriétés positionnent SixGe(1-x)-2H comme un « matériau miracle» parmi les semi-conducteurs du groupe IV, avec des applications prometteuses dans l'émission lumineuse dans le moyen infrarouge et la détection sur des plateformes en silicium.Malgré les progrès récents, la synthèse de volumes importants de Ge-2H de haute qualité reste un défi. Jusqu'à présent, Le Ge-2H a été synthétisé sous forme de nanodomaines issus de transformations de phase induites par cisaillement, de nanofils cœur/enveloppe et de nanobranches. Ces approches limitent les volumes actifs et la fabrication évolutive de dispositifs. La synthèse de couches planaires de SixGe(1-x)-2H de haute qualité, avec un dopage contrôlé, est essentielle pour permettre une intégration optimale.Cette thèse vise à ouvrir la voie à la synthèse de couches planes de Ge hexagonal en utilisant l'épitaxie en phase vapeur sous ultra-haut vide (UHV-VPE) sur des substrats hexagonaux plan-m du groupe II-VI, tels que CdS-2H et ZnS-4H. Les travaux incluent le développement de techniques de préparation de surface pour les composés II-VI et des études détaillées sur la formation de structures hexagonales dans des matériaux tels que GaAs-4H, ZnS-2H via MOCVD, et le Ge dans les phases hexagonales 2H et 4H.Une étape préliminaire cruciale a consisté à préparer les surfaces des substrats, car leur qualité impacte directement celle des couches épitaxiées. La préparation des surfaces a inclus un polissage mecano-chimique avec une solution de Br2-MeOH pour éliminer les contaminants de surface. Les défis liés aux propriétés thermiques des substrats CdS-2H et ZnS-4H ont été abordés, notamment la désorption des composés II-VI et la formation de « negative whiskers » au-dessus de 500°C.La croissance épitaxiale par UHV-VPE a posé des contraintes de sélectivité sur les substrats II-VI, ce qui a conduit à explorer des configurations alternatives de croissance, telles que l'utilisation de couches buffer. Cette thèse présente la première synthèse d'une couche de GaAs dans la structure hexagonale 4H par épitaxie sur un substrat ZnS-4H plan-m, ainsi qu'une première caractérisation des défauts d'empilement basal dans cette couche. La faisabilité de la synthèse de Ge sur GaAs-4H a également été étudiée. Une part importante du travail a été consacrée à la croissance sur les substrats CdS-2H, démontrant la première couche de Ge avec des régions nanométriques de Ge-2H, offrant une preuve de concept pour la réplication de structures Ge-2H sur des surfaces II-VI sur plan-m. L'optimisation du processus a conduit au développement de couches tampons ZnS-2H sur CdS-2H via MOCVD. Une étude approfondie a montré que la température de croissance impacte fortement la qualité cristalline des substrats CdS. Les couches de ZnS cultivées à 360°C ont révélé une structure hexagonale pure avec une orientation épitaxiale optimale. La relaxation des contraintes s'est produite via des dislocations de réseau à l'interface, en raison des désaccords de maille de 7,63 % et 6,83 % le long des axes a et c, formant des défauts d'empilement basal et prismatique sur les plans {112 ̅0}. Enfin, pour appuyer notre étude, cette thèse présente des preuves démontrant la synthèse d'une couche de Ge avec une phase hexagonale partielle
Silicon and Germanium crystallizing in the cubic diamond (denoted 3C) structure, have been the cornerstone of the electronic industry due to their inherent properties. However, metastable crystal phase engineering has emerged as a powerful method for tuning electronic band structures and conduction properties, enabling new functionalities while maintaining chemical compatibility. Notably, Germanium within the hexagonal 2H phase exhibits a direct bandgap of 0.38 eV. The alloy SixGe(1-x)-2H demonstrates strong light emission with a tunable wavelength ranging from 1.8 µm to 3.5 µm, depending on silicon concentration (40% to 0%). These properties position SixGe(1-x)-2H as a "holy grail material" among group IV semiconductors, with promising applications in mid-infrared light emission (e.g., LEDs and lasers) and detection on silicon platform.Despite recent progress, synthesizing large volumes of high-quality Ge-2H remains a challenge. Until now, Ge-2H has been limited to nanostructures, including nanodomains formed by shear-induced phase transformation, core/shell nanowires, and nanobranches. These approaches restrict active volumes, hindering basic property investigation and scalable device manufacturing. Achieving high-quality planar crystals with controlled doping is essential for advancing SixGe(1-x)-2H integration.This thesis aims to pioneer the synthesis of planar layers of hexagonal Ge using Ultra High Vacuum - Vapor Phase Epitaxy (UHV-VPE) on hexagonal m-plane II-VI substrates such as CdS-2H and ZnS-4H. The work includes developing surface preparation techniques for II-VI compounds and conducting detailed studies on hexagonal structure formation in materials such as GaAs-4H, ZnS-2H (grown via Metal-Organic Chemical Vapor Deposition, MOCVD), and Ge in both 2H and 4H hexagonal phases.A crucial preliminary step involved preparing substrate surfaces, as their quality directly impacts the crystalline quality of the epitaxial layers. Surface preparation included chemical-mechanical polishing with a Br2-MeOH solution to remove surface contaminants, confirmed through XPS analysis. Challenges related to the thermal properties of CdS-2H and ZnS-4H substrates were addressed, including desorption of II-VI compounds and the formation of negative whiskers above 500°C.Epitaxial growth by UHV-VPE posed selectivity constraints on II-VI substrates, prompting the exploration of alternative growth configurations, such as using buffer template layers. This thesis presents the first synthesis of a GaAs layer in the 4H hexagonal structure grown by epitaxy on ZnS-4H m-plane substrate, along with a first characterization of basal stacking faults (BSFs) in this layer. The feasibility of synthesizing Ge on GaAs-4H was also investigated. A significant part of the work was dedicated to growth on the CdS-2H substrates, demonstrating the first Ge layer with nanoscale regions of Ge-2H epitaxy, providing proof of concept for structure replication of Ge-2H on II-VI m-plane surfaces. However, amorphous and highly defective regions were also observed. Process optimization led to the development of ZnS-2H template layers on CdS-2H using MOCVD, circumventing constraints of direct growth on CdS. A thorough investigation of growth regimes revealed a strong impact of growth temperature on the CdS substrate surface, significantly influencing crystalline quality. m-plane ZnS layers grown at 360°C exhibited a pure hexagonal structure with excellent epitaxial orientation relative to CdS-WZ substrates. Strain relaxation occurred through misfit dislocations at the interface due to lattice mismatches of 7.63% and 6.83% along the a- and c-axes, forming basal and prismatic stacking faults on {11-20} planes. Finally, as further proof of concept, the thesis presents evidence supporting the synthesis of a Ge layer with a partial hexagonal phase

Instantaneous time-of-flight spectrometry of neutrons (nToF) and γ‑spectrometry from nuclear reactions generated by nanosecond proton and 12C ion bunches collectively accelerated in a Luce diode at a voltage across the diode of 200–300 kV has been thoroughly researched. A two-channel γ‑spectrometer with time resolution of 2.5 ns enables a prompt control of number and energy of collectively accelerated protons in their separate bunches dumped into a sustainable and refractory B4C target. Combination of nuclear reactions 10B(p,αγ)7Be, 12C(p,γ)13N, and 11B(p,γ)12C was used to characterize the intense nanosecond proton bunches with energy and number per shot in excess of 500–750 keV and 6∙1014, respectively. The radioactivity of 7Be and 13N radionuclides was measured with a conventional HP Ge detector to calibrate the prompt technique. The threshold nuclear reaction 11B(p,n)11C was used to perform nToF spectrometry of high-energy protons bunches with energy higher than 3.02 MeV, while 12C(d,n)13N and 2H(12C,n)13N reactions were used to control deuteron and 12C ion bunches.