Analyzing the surface passivity effect of germanium oxynitride:a comprehensive approach through first principles simulation and interface state density

High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achieving an extremely low energy threshold.In this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface passivation.Theoretical calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface state.Based on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio structure.The microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state density.The mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.

Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.

Yunnan Chihong Zinc & Germanium Co.,Ltd.Invested RMB 300 Million for Germanium Project with Output 30 Tons/Year

Recently,Yunnan Chihong Zinc & Germanium Co.,Ltd.,an A-share listed company held by Yunnan Metallurgical Group Co.,Ltd.,kicked off its construction of a project for comprehen- sive utilization of lead-zinc associated metal germanium resources to be output at 30 tons/year.It is introduced that the

Yunnan Chihong Zinc ﹠ Germanium Co., Ltd Conducts a Series of Frequent Acquisition to Aim at the Target of 10 Million tons of Resources Reserve

At the beginning of this year,Chihong Zinc﹠Germanium proposed to create"Ten billion Chihong,the international benchmark",and to realize the goal of 10 million tons of domestic retained metal reserve of lead and zinc by the end of the national twelfth five-year-plan.When taking a retrospect at the end of this year,Chihong Zinc﹠Germanium has made its early vision--the strategy"to step out"

Effect of germanium on electrochemical performance of chain-like Co-P anode material for Ni/Co rechargeable batteries

Co-P （4.9% P） powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co-P and germanium powders were mixed at various mass ratios to form Co-P composite electrodes. Charge and discharge test and electrochemical impedance spectroscopy （EIS） were carried out to investigate the electrochemical performance, which can be significantly improved by the addition of germanium. For instance, when the mass ratio of Co-P powders to germanium is 5：1, the sample electrode shows a reversible discharge capacity of 350.3 mA·h/g and a high capacity retention rate of 95.9% after 50 cycles. The results of cyclic voltammmetry （CV） show the reaction mechanism of Co/Co（OH）2 within Co-P composite electrodes and EIS indicates that this electrode shows a low charge-transfer resistance, facilitating the oxidation of Co to Co（OH）2.

Study on cosmogenic radioactive production in germanium as a background for future rare event search experiments

Rare event search experiments are one of the most important topics in the field of fundamental physics,and high-purity germanium(HPGe)detectors with an ultralow radioactive background are frequently used for such experiments.However,cosmogenic activation contaminates germanium crystals during transport and storage.In this study,we investigated the movable shielding containers of HPGe crystals using Geant4 and CRY Monte Carlo simulations.The production rates of 68Ge,65Zn,60Co,55Fe,and 3H were obtained individually for different types of cosmic rays.The validity of the simulation was confirmed through a comparison with the available experimental data.Based on this simulation,we found that the interactions induced by neutrons contribute to approximately 90%of the production rate of cosmogenic activation.In addition,by adding an optimized shielding structure,the production rates of cosmogenic radionuclides are reduced by about one order of magnitude.Our results show that it is feasible to use a shielding container to reduce the cosmogenic radioactivity produced during the transport and storage of high-purity germanium on the ground.

Continuous electrodeposition of silicon and germanium micro/nanowires from their oxides precursors in molten salt

In recent years,silicon(Si)and germanium(Ge)materials have been considered as promising highperformance anode materials for lithium-ion batteries due to their high theoretical capacities.It is of great importance to design and synthesize micro/nanostructured Si and Ge materials.In this work,we demonstrated that Si,Ge and SiGe micro/nanowires can be continuously synthesized from their oxides precursors through molten salt electrodeposition.The electrochemical synthesis processes have been investigated systematically,and the deposited Si,Ge and SiGe micro/nanowires have been characterized and compared.The results show that the micro/nanostructured Si and Ge materials with tunable morphology can be facilely and continuously produced via molten salt electrodeposition.The electrodeposition process generally includes calcium oxide-assisted dissolution and electrodeposition processes,and the morphologies of the deposited Si and Ge products can be controlled by varying conditions.Si micro/nanowires,Si films,Ge micro/nanowires,and Ge particles can be continuously synthesized in a controlled manner.

Recovering germanium from coal ash by chlorination with ammonium chloride

A new process of enriching germanium from coal ash was developed. The processinvolves in mixing the coal ash and ammonium chloride and then roasting the mixture to producegermanium chloride that is then absorbed by dilute hydrochloric acid and hydrolyzed to germaniumoxide. The germanium recovery reached to 80.2% at the optimum condition: mass ratio of NH_4Cl/coalash is 0.15, roasting temperature 400℃ and roasting time 90 min.

Kinetics of recovering germanium from lignite ash with chlorinating roasting methods

A process of recovering Ge by chlorinating masting was put forward. GeCl4 was separated and recovered from lignite ash because of its low boiling point. Kinetic analysis indicates that the chlorinating roasting process fits with the unreacted-core shrinking model and the reaction rate equation corresponds to 1 - 2a/3 - （1 - a）2/3 = kt. The apparent activation energy Ea is calculated to be 22.36 kJ·mol^-1. The diffusion of product layer serves as the rate-controlling step in this process. When the roasting temperature is 250℃, the roasting time is 60 min, the con- centration of hydrochloric acid is 10 mol/L, and the ratio of liquid to solid is 10 （mHCl/ash = 10）, and 90% Ge in lignite ash can be recovered.

Identification of anomalous fast bulk events in a p-type point-contact germanium detector

The ultralow detection threshold,ultralow intrinsic background,and excellent energy resolution of ptype point-contact germanium detectors are important for rare-event searches,in particular for the detection of direct dark matter interactions,coherent elastic neutrino-nucleus scattering,and neutrinoless double beta decay.Anomalous bulk events with an extremely fast rise time are observed in the CDEX-1B detector.We report a method of extracting fast bulk events from bulk events using a pulse shape simulation and reconstructed source experiment signature.Calibration data and the distribution of X-rays generated by intrinsic radioactivity verified that the fast bulk experienced a single hit near the passivation layer.The performance of this germanium detector indicates that it is capable of single-hit bulk spatial resolution and thus provides a background removal technique.

High‑accuracy measurement of Compton scattering in germanium for dark matter searches

Compton scattering with bound electrons contributes to a significant atomic effect in low-momentum transfer,yielding background structures in direct light dark matter searches as well as low-energy rare event experiments.We report the measurement of Compton scattering in low-momentum transfer by implementing a 10-g germanium detector bombarded by a^(137)Cs source with a radioactivity of 8.7 mCi and a scatter photon captured by a cylindrical NaI(Tl)detector.A fully relativistic impulse approximation combined with multi-configuration Dirac–Fock wavefunctions was evaluated,and the scattering function of Geant4 software was replaced by our calculation results.Our measurements show that the Livermore model with the modified scattering function in Geant4 is in good agreement with the experimental data.It is also revealed that atomic many-body effects significantly influence Compton scattering for low-momentum transfer(sub-keV energy transfer).

High-Performance Germanium Waveguide Photodetectors on Silicon

Germanium waveguide photodetectors with 4μm widths and various lengths are fabricated on silicon-on-insulator substrates by selective epitaxial growth.The dependence of the germanium layer length on the responsivit.y and bandwidth of the photodetectors is studied.The optimal length of the germanium layer to achieve high bandwidth is found to be approximately 8μm.For the 4×8μm^2 photodetector,the dark current density is as low as 5 mA/cm^2 at^-1 V.At a bias of-1 V,the 1550 nm optical responsivity is as high as 0.82 A/W.Bandwidth as high as 29 GHz is obtained at-4 V.Clear opened eye diagrams at 50 Gbits/s are demonstrated at 1550 nm.

High performance silicon waveguide germanium photodetector

High-performance Ge-on-SOI p–i–n waveguide photodetectors with different sizes were fabricated. The performances, in terms of dark-current, photo current responsivity and 3-d B bandwidth, were well studied. A responsivity of 0.842 A/W at 1550 nm and dark current of 70 n A was measured from this detector at-1 V. The detector with a size of4 μm×10 μm demonstrated an optical band width of 19 GHz at-5 V for 1550 nm. Both the experimental results and the finite-difference time domain simulation show that, when the device size is above a certain threshold, the absorption is not sensitively dependent on such designing parameters as the width and length of the photodetector.

Ab initio Study of Anharmonic Force Field and Spectroscopic Constants for Germanium Dichloride

Ab initio study of the equilibrium structure, spectroscopy constants, and anharmonic force field for several isotopomers of germanium dichloride （70GeCl2, 72GECl2, and 76GeCl2） have been carried out at the MP2 and CCSD（T） levels of theory using cc-pVTZ basis set. The cal- culated geometries, rotational constants, vibration-rotation interaction constants, harmonic frequencies, anharmonic constants, quartic and sextic centrifugal distortion constants, cubic and quartic force constants are compared with experimental data. For small mass differences of the Ge isotopes, the isotopic effects for germanium dichloride are much weaker. The agreements are satisfactory for these two methods, but the deviations of CCSD（T） results are slightly larger than that of MP2, because of CCSD（T）＇s inadequate treatment of electron correlation in hypervalent Cl atom.

Spatial distribution characteristics and main controlling factors of germanium in soil of northern Dabie Mountains, China

With the increasing application of germanium(Ge)elements in modern industry,military and medical health industries,especially with the growing demand for Ge-rich agricultural products,the study of Ge-rich soil has become particularly important,but the enrichment pattern and control factors of Ge-rich soil are still not well understood due to the high dispersion and high migration of Ge-rich soil.In this paper,495 surface soil(0-20 cm)and 149 deep soil(150-200 cm)samples were collected from the northern foothills of Dabie Mountain using a double-layer grid layout,and the spatial distribution and enrichment characteristics of Ge were studied by high-resolution method,and the controlling factors affecting the distribution of Ge-rich soil was analyzed by geo-statistics and spatial analogy.The results show an average Ge content of 1.34 mg/kg for the surface and 1.36 mg/kg for the deep soil.In the assessment grade classification of surface and deep soil for Ge,the abundant and sub-abundant grades account for 37.97%and 31.70%,respectively,covering 752 km2 and 634 km2.Surface Ge-rich regions are distributed in concentrated strips in the north-central part of the studied region,and there is no clear pattern in the spatial distribution of deep soils.In the areas under study,such as Fenlukou,Dingji,and Jiangjiadian,the surface soil is very rich in Ge and has a high enrichment factor,which is valuable for agricultural development.In surface soils,river deposits and shallow metamorphic rock parent materials have the highest content of Ge,while in deep soils,the highest content has been found in the parent material of moderately acidic rock.Both surface and deep soils have the highest Ge content in purple paddy soils and plain areas.The source of Ge in the soils of the study area is most influenced by the lithology of the soil-forming parent material,while the distribution of Ge in the surface soils is jointly influenced by pH,SiO_(2),TFe_(2)O_(3),and Al_(2)O_(3) in the soil.This study has implications for understanding the enrichment pattern of Ge in soil and its controlling factors as well as for the development of Ge-rich agricultural products.

Recovery of germanium from lignite by microorganism

The recovery of Ge from lignite by microorganism includes two stages: (1) thebreaking-down of Ge complex of humus in lignite into simple compounds assisted by microorganism;(2) the desorption of Ge compounds from the lignite. The recovery rate of Ge has been enhanced by 14percent since the discovery of adsorption and desorption of Ge from coal. The effects of pH,leaching agents, and coal size on the recovery of Ge were experimentally investigated, and theoptimized process parameters were obtained. The reaction heat of Ge adsorption and desorption inlignite was determined. It is about 23-53 kJ/mol, which reveals that the adsorption belongs tophysical process. The recovery rate of Ge from lignite with direct microorganism leaching can reachabout 85 percent, which is higher than that of 60 percent reported elsewhere. A potential processfor leaching Ge in lignite was suggested.

SYNTHESIS AND CHARACTERIZATION OF AMINO－ACID SCHIFF BASE AND ITS GERMANIUM COMPLEX

Condensation of eqqimolar quantities of salicylaldehyde and a-amino acid (glycine, alanine, valine, leucine, Phenylalanine, serine, cysteine) in absolute Methanol-KOH gives the amino acid Schiff base[1]. Its germanium tetrachloride adducts of the type GeCL. (sal=aa.k)2 have been prepared in absolute mothanol[2]and characterized by elemental analyses, conductance measurements, IR and 1H-NMR spectra, electronic spectra, cyclic voltammetry and thermal analyses. etc.

SYNTHESIS OF ORGANOGERMANE OLIGOMERS VIA LIGAND SUBSTITUTION POLYMERIZATION FROM 1, 4-DIOXANE COMPLEX OF GERMANIUM DICHLORIDE

Some organogermanium oligomers with different side groups were synthesized via ligand substitution polymerization from I, l-dioxane complex of germanium dichloride with different organolithium compounds. The oligomers were isolated through either precipitation from methanol or extraction using toluene with a yield of no less than 50%. The weight average molecular weight (M-w) of the oligomers is ranging from 1.4 x 10(3) to 5.9 x 10(3) depending on the type and alkyl length of the organolithium compounds used.

Thermal Analysis Simulation of Germanium Zone Refining Process Assuming a Constant Radio-Frequency Heating Source

Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged througll the tube. A narrow section of the, boat is assmned to be exposed to a constant heat rate produced b v an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of tile molten zone, required power and temperature gradient in the system.

Phosphorus diffusion and activation in fluorine co-implanted germanium after excimer laser annealing

The diffusion and the activation of phosphorus in phosphorus and fluorine co-implanted Ge after being annealed by excimer laser are investigated.The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation.Moreover,the rapid thermal annealing process is utilized to evaluate and verify the role of fluorine element.During the initial annealing of co-implanted Ge,it is easier to form high bonding energy FnVm clusters which can stabilize the excess vacancies,resulting in the reduced vacancy-assisted diffusion of phosphorus.The maximum activation concentration of about 4.4 ×10^(20) cm^(-3) with a reduced diffusion length and dopant loss is achieved in co-implanted Ge that is annealed at a tailored laser fluence of 175 mJ/cm^(2).The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its applications in the scaled Ge MOSFET technology and other devices.