Ge Reaction Research Articles

^{74}Ge(n,gamma ) cross section below 70 keV measured at n_TOF CERN

Neutron capture reaction cross sections on ^{74}Ge are of importance to determine ^{74}Ge production during the astrophysical slow neutron capture process. We present new resonance data on ^{74}Ge(n,gamma ) reactions below 70 keV neutron energy. We calculate Maxwellian averaged cross sections, combining our data below 70 keV with evaluated cross sections at higher neutron energies. Our stellar cross sections are in agreement with a previous activation measurement performed at Forschungszentrum Karlsruhe by Marganiec et al., once their data has been re-normalised to account for an update in the reference cross section used in that experiment.

Isomeric cross section study of neutron induced reactions on Ge isotopes

Cross sections for the70,76Ge(n,2n),72,73Ge(n,p) and72,74Ge(n,α) reactions have been measured at the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR Demokritos, using the activation technique. Neutron beams have been produced in the ~16-20 MeV energy region, by means of the3H(d,n)4He reaction. The maximum flux has been determined to be of the order of 105n/cm2s, while the flux variation of the neutron beam was monitored by using a BF3 detector. The cross section has been deduced with respect to the27Al(n,α)24Na and93Nb(n,2n)92mNb reference reactions. The contaminations from reactions induced on neighboring Ge isotopes and leading to the same residual nucleus, have been taken into account. After the end of the irradiations, the activity induced by the neutron beams at the targets and reference foils, has been measured by HPGe detectors. Statistical model calculations using the EMPIRE code were performed on the data measured in this work as well as on data reported in literature.

Statistical model calculations of 72,73Ge(n,p) and 72,74Ge(n,α) reactions on natural Ge

Systematic experimental and theoretical investigations of the 72,73Ge(n,p)72,73 Ga and 72,74Ge(n,α)69,71Znm reaction cross sections are presented in the energy range from thresh- old to about 17 MeV neutron energy. The above reaction cross sections were measured from 8.8 to 11.4 MeV by using the activation method, relative to the 27Al(n,α)24Na refer- ence reaction. The quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction at the 5 MV VdG Tandem T11/25 accelerator of NCSR “Demokritos”. Statisti- cal model calculations using the code EMPIRE-II (version 2.19) taking into consideration pre-equilibrium emission were performed on the data measured in this work as well as on data reported in literature.

Promoting effect of Ge on Pt-based catalysts for dehydrogenation of propane to propylene

In this study, a Ge-promoted Pt catalyst with enhanced performance for propane dehydrogenation (PDH) has been developed. Pt0.5-Ge1.5/Al2O3 shows outstanding stability and performance (deactivation parameter: 0.10 1/h, propylene selectivity: 97.2%) in comparison with the monometallic Pt0.5/Al2O3 catalyst (deactivation parameter: 0.42 1/h, propylene selectivity: 56.9%). Effects of Ge loading (1.0%, 1.5%, 2.0%), reduction temperature and reaction temperature were investigated. Characterization techniques including XPS, BET, CO-DRIFTS, CO chemisorption, TG/DTA, RAMAN, XANES, and NH3-TPD were applied to study the fresh and spent catalysts. The modification of Pt structure and its electronic properties is ascribed to an alloy formation between Pt and Ge. Due to this alloy formation, Ge dilutes Pt surface, breaking the Pt ensembles and, at the same time, withdrawing electrons from Pt. As a result of these geometric and electronic modifications, superior performance of Pt0.5-Ge1.5/Al2O3 has been achieved.

Interplay of neutron transfer and collective degrees of freedom in the fusion dynamics of 16O +76Ge and 18O +74Ge reactions

This work examined the fusion dynamics of [Formula: see text] and [Formula: see text] reactions within the framework of the static Woods–Saxon potential model, the energy dependent Woods–Saxon potential (EDWSP) model and coupled channel formulation. The effects of inelastic surface excitations, static deformation of colliding pairs and /or neutron transfer channels on fusion process are investigated through the coupled channel method. The calculations based upon static Woods–Saxon potential in conjunction with one-dimensional Wong formula strongly under predict the fusion data of [Formula: see text] and [Formula: see text] reactions at sub-barrier energies. However, such discrepancies are removed if one uses couplings to nuclear structure degrees of freedom of reacting nuclei. The coupled channel calculations obtained by considering the vibrational nature of the colliding nuclei fairly reproduce the fusion data of [Formula: see text] reactions. For this reaction, the neutron transfer channels, which are expected to influence strongly the fusion yields at below barrier energies, in reality contribute very weakly to fusion process. While in case of [Formula: see text] reaction, the consideration of vibrational couplings as well as the rotational couplings for target provides a reasonable explanation to the fusion cross-section data at near and above barrier energies. In distinction, the energy dependence in the nucleus–nucleus potential causes barrier modulation effects and subsequently modifies the barrier profile of the interaction barrier in such a way that the effective fusion barrier between the colliding pair reduces. This ultimately brings larger fusion cross-sections over the outcomes of one-dimensional barrier penetration model and the EDWSP model based calculations appreciably explained the fusion dynamics of chosen reaction at energy spanning around the Coulomb barrier. Both models (EDWSP and coupled channel model) lead to barrier lowering effects and modeled quantum tunneling in different way, henceforth, adequately explore the fusion dynamics of the studied reactions in near and above barrier energy regions.

Colloidal Silicon–Germanium Nanorod Heterostructures

Colloidal nanorods with axial Si and Ge heterojunction segments were produced by solution–liquid–solid (SLS) growth using Sn as a seed metal and trisilane and diphenylgermane as Si and Ge reactants. The low solubility of Si and Ge in Sn helps to generate abrupt Si–Ge heterojunction interfaces. To control the composition of the nanorods, it was also necessary to limit an undesired side reaction between the Ge reaction byproduct tetraphenylgermane and trisilane. High-resolution transmission electron microscopy reveals that the Si–Ge interfaces are epitaxial, which gives rise to a significant amount of bond strain resulting in interfacial misfit dislocations that nucleate stacking faults in the nanorods.

Statistical gamma-ray decay studies at iThemba LABS

A program to study the γ-ray decay from the region of high-level density has been established at iThemba LABS, where a high-resolution gamma-ray detector array is used in conjunction with silicon particle-telescopes. Results from two recent projects are presented: 1) The 74 Ge(α,α′γ) reaction was used to investigate the Pygmy Dipole Resonance. The results were compared to (γ,γ′) data and indicate that the dipole states split into mixed isospin and relatively pure isovector excitations. 2) Data from the 95 Mo(d,p) reaction were used to develop a novel method for the determination of spins for low-lying discrete levels utilizing statistical γ-ray decay in the vicinity of the neutron separation energy. These results provide insight into the competition of (γ,n) and (γ,γ′) reactions and highlights the need to correct for angular momentum barrier effects.

First stages of Ni reaction with the Si(Ge) alloy

The Si(Ge) alloy is currently used in the Complementary Metal Oxide Semiconductor (CMOS) technology, improving device performances, decreasing power consumption, and allowing stress engineering in Si-based devices. If Si(Ge) is used in transistors' source, drain and gate, it is necessary to create ohmic contacts between the first-level metal and Si(Ge). In the current Si-based CMOS technology, ohmic contacts are created via the reaction of a thin Ni(Pt) layer with doped-Si, aiming to form a thin NiSi layer on the Si substrate. A similar process should be used on Si(Ge). In this work, the first stages of Ni reaction with Si(Ge) is investigated using high resolution transmission electron microscopy and laser-assisted atom probe tomography. The first stage of Ni/Si(Ge) reaction leads to the formation of a germano-silicide layer made of Nip(Si1−xGex)q nano-grains exhibiting different structures and compositions. The formation of Nip(Si1−xGex)q phases occurs at temperatures as low as 60 °C. The germano-silicide grains exhibit coherent interfaces with the Si(Ge) layer, and during their growth, a fraction of the Ge atoms initially located in Si(Ge) is pushed from the Nip(Si1−xGex)q/Si(Ge) interface into the Si(Ge) layer, leading to Ge accumulation at this interface. This phenomenon can cause Ge accumulation up to 100%, promoting the incorporation of Ge-pure nanometric inclusions inside the germano-silicide layer.

Estimation method of planetary fast neutron flux by a Ge gamma-ray spectrometer

An intensity map of lunar fast neutrons (LFNs) and their temporal variation has been estimated by fitting “sawtooth” peaks in the energy spectra of lunar gamma rays observed by the Kaguya (SELENE) Gamma Ray Spectrometer (GRS) consisting of a high-purity germanium (HPGe) detector with a BGO scintillator. While an ordinary peak in the spectrum is produced by only gamma ray lines, the sawtooth peak is produced by gamma ray lines and recoil nuclei in the detector by Ge(n,n′γ) reaction. We develop a model for the shape of the sawtooth peak and apply it to fit sawtooth peaks together with ordinary peaks in actual observed spectra on the Moon. The temporal variation of LFNs is synchronous with that of galactic cosmic rays (GCRs), and the global distribution of fast neutrons on the lunar surface agrees well with the past observation reported by the Neutron Spectrometer aboard Lunar Prospector. Based on these results, a new method is established to estimate the flux of fast neutrons by fitting sawtooth peaks on the gamma ray spectrum observed by the HPGe detector.

Mn Diffusion and Reactive Diffusion in Ge: Spintronic Applications

In this paper, we report investigations concerning the fabrication of a diluted Ge (Mn) solution using solid state Mn diffusion, and Mn/Ge reactive diffusion for spintronic applications. The study of Mn diffusion shows that the quasi-totality of the incorporated Mn atoms occupies Ge substitutional sites and probably exhibits two negative elementary charges. The solubility limit of Mn in Ge is comprised between 0.7 and 0.9 % (T  600 °C). We show that substitutional Mn atoms are not ferromagnetic in Ge and consequently that Ge (Mn) diluted magnetic semiconductor can not be produced. Beside the ferromagnetic signal from Mn5Ge3, ferromagnetic signals detected in the samples could be always attributed to surface or bulk Mn-Ge clusters. Furthermore, we show that the CMOS Salicide process is potentially applicable to Mn5Ge3 nanolayer fabrication on Ge for spintronic applications. During Mn (thin-film)/Ge reaction, Mn5Ge3 is the first phase to form, being thermally stable up to 310 °C and exhibiting ferromagnetic properties up to TC ~ 300 K.

Inelastic neutron scattering studies of76Ge and76Se: relevance to elevance to neutrinoless double-β decay

Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched 76 Ge and 76 Se scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, γ-ray cross sections for the 76 Ge(n,n′γ) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of γ rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double β decay of 76 Ge. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV γ ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of ~0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported γ rays from levels in 76 Ge can be found in the 2039-keV region.

Novel technique for constraining r-process (n, γ) reaction rates.

A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r process. As a proof of principle, the γ spectra from the β decay of ^{76}Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and γ-ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the ^{75}Ge(n,γ)^{76}Ge cross section and reaction rate.

Proton pair correlations and the neutrinoless double-βdecay of76Ge

Proton pair correlations relevant for the neutrinoless double-$\ensuremath{\beta}$ decay of ${}^{76}$Ge have been probed via the ${}^{74,76}$Ge(${}^{3}$He,$n$) reactions at 16 MeV. No evidence for pairing vibrations in either nucleus is observed at sensitivity limits of $\ensuremath{\sim}$6$%$ and $\ensuremath{\sim}$19$%$ of the ground-state strength in ${}^{76}$Se and ${}^{78}$Se, respectively. These results are relevant for the understanding of matrix elements for neutrinoless double-$\ensuremath{\beta}$ decay. The lack of pairing vibrations is consistent with a simple BCS structure for the ground states of ${}^{76}$Ge and ${}^{76}$Se, assumed in quasiparticle random phase approximation (QRPA) models of the process.

High-spin study of the shell model nucleus88Y49

The near-yrast structure of the near-magic, odd-odd nucleus, ${}_{39}^{88}$Y${}_{49}$, has been studied into the high-spin regime. Investigations were performed at the Wright Nuclear Structure Laboratory, Yale University, using the ${}^{74}$Ge(${}^{18}$O,$p3n$) and ${}^{76}$Ge(${}^{18}$O,$p5n$) fusion-evaporation reactions at beam energies of 60 and 90 MeV, respectively. Gamma-ray energy coincidence analyses using both double (${\ensuremath{\gamma}}^{2}$) and triple (${\ensuremath{\gamma}}^{3}$) fold coincidences, together with angular correlation measurements, have been used to extend the previously reported level scheme to an excitation energy of 8.6 MeV and a spin and parity of 19${}^{(\ensuremath{-})}$. The presented level scheme is compared with predictions of a truncated valence space shell-model calculation, which assumes an inert ${}^{56}$Ni core with proton and neutron excitations allowed within the ${f}_{5/2}$, ${p}_{3/2}$, ${p}_{1/2}$, and ${g}_{9/2}$ single-particle states. The shell-model calculations show a reasonable comparison with the experimental data for the yrast, positive-parity states up to spin 18 $\ensuremath{\hbar}$, with larger variations evident for negative-parity states with spins greater than 16 $\ensuremath{\hbar}$. In spite of a significant increase in angular momentum input associated with the thin target ${}^{76}$Ge(${}^{18}$O,$p5n$) reaction channel, as compared to the backed target data using the ${}^{74}$Ge target, no additional discrete states were identified in the former data set, suggesting that the level scheme for this nucleus fragments significantly above the observed states, possibly indicating cross-shell excitations becoming dominant for $Ig$19 $\ensuremath{\hbar}$.

A method to estimate a contribution of Ge(n,n′) reaction to the low-energy part of gamma spectra of HPGe detectors

Long-time background spectra of a well-shielded HPGe detector are recorded in order to estimate the contribution of inelastic neutron scattering on Ge nuclei in the low-energy part of the spectra, mainly influenced by elastic neutron collisions. It is shown that using intensities of several asymmetric peaks characteristic of Ge(n,n′) reactions and some properties of detectors (ability for total absorption or total transmission of gamma photons emitted during de-excitation of Ge nuclei) the contribution of Ge(n,n′) reactions to the low-energy part of spectra can be evaluated. The obtained result is in good agreement with results of simulations available in the literature.

An unusual phenomenon of surface reaction observed during Ge overgrowth on Mn5Ge3/Ge(111) heterostructures

The Mn5Ge3 compound, thanks to its room-temperature ferromagnetism, metallic character and ability to epitaxially grow on germanium, acts as a potential candidate for spin injection into group-IV semiconductors. Understanding and controlling Ge overgrowth behaviour on Mn5Ge3/Ge heterostructures represents a crucial step to realize Ge/Mn5Ge3/Ge multilayers for numerous spintronic applications. Here, we have combined structural and morphological characterizations with magnetic analyses to study the mechanisms of Ge overgrowth on epitaxial Mn5Ge3 layers in the temperature range of 450–550 °C. It is found that deposited Ge instantly reacts with Mn to form a Mn5Ge3 surface layer, which, acting as a surfactant, continuously floats upwards from the growing surface to a distance larger than 70 nm. New Ge layers are successively formed underneath, allowing such a floating Mn5Ge3 surface layer to be stabilized by epitaxy. These observations can be considered as a typical example in which the stabilization of metastable thin films by epitaxy can overcome thermodynamic equilibrium. We have also investigated the effect of carbon adsorption on the top of the Mn5Ge3 layer prior to Ge deposition to control the Mn:Ge reaction. It is shown that adsorbed carbon effectively reduces the out-diffusion of Mn from Mn5Ge3, allowing Ge layers to stack up on top of Mn5Ge3. However, at temperatures of 450–550 °C, carbon may react with Mn to form manganese carbides and the resulting Ge overlayers are found to change their orientation from the (111) plane to the (001) plane, which has a higher surface energy. Finally, a strategy to realize Ge/Mn5Ge3/Ge multilayers will be addressed.

High-Performance Charge-Trapping Flash Memory Device With an Ultrathin 2.5-nm Equivalent- $\hbox{Si}_{3}\hbox{N}_{4}$-Thickness Trapping Layer

We made the MoN-[SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> - LaAlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ]-[Ge-HfON]- [LaAlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ]-Si charge-trapping (CT) Flash device with a record-thinnest 2.5-nm equivalent-Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -thickness trapping layer, a large 4.4-V initial memory window, a 3.2-V ten-year extrapolated retention window at 125 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, and a 3.6-V endurance window at 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles, under very fast 100 μs and low ±16-V program/erase pulses. These were achieved using Ge reaction with a HfON trapping layer for better CT and retention.

Level studies of 71 Ge via 71 Ga (P, nγ) 71 Ge reaction and density of discrete levels in 71 Ge

The excited states of 71Ge have been investigated via the 71Ga (P, n) 71Ge reaction with the proton beam energies from 2.5 to 4.3 MeV. The parameters of the nuclear level density formula have been determined from the extensive and complete level scheme for 71Ge. The Bethe formula for the back-shifted Fermi gas model and the constant temperature model are compared with the experimental level densities. Key words: Level schemes of 71Ge, 71Ga (P, n) 71Ge reaction, angular distribution, Fermi gas model.

Cross sections for (d–t) neutron interaction with germanium isotopes

Abstract The cross sections for ( n , x ) reactions with Ge isotopes were measured at ( d – t ) neutron energies around 14 MeV with the activation technique using metal discs of natural composition. Calculations of detector efficiency, incident neutron spectrum and correction factors were performed with the Monte Carlo technique (MCNP4C code). Cross sections data are presented for 70 Ge( n , 2 n ) 69 Ge, 74 Ge( n , α ) 71 m Zn, 76 Ge( n , 2 n ) 75( m + g ) Ge, 70 Ge( n , p ) 70 Ga and 72 Ge( n , 2 n ) 71 g Ge reactions. The cross section results for 72 Ge( n , 2 n ) 71 g Ge reaction were reported for the first time. Some other cross sections were obtained with higher precision, including the 70 Ge( n , p ) 70 Ga reaction. Theoretical calculations of excitation functions were performed with the TALYS-1.0 code and compared with the experimental cross section values. Data were included in the EXFOR database.

ChemInform Abstract: Crystal Structure and Physical Properties of the New Antimonide Hf3Cu2Ge3.58Sb1.42.

AbstractThe new title compound is synthesized by arc melting of a mixture of Hf, Cu, and Ge (3:2:3.58) and subsequent reaction with Sb (1323 K, 12 h).