Germanium Oxide Research Articles

Eco‐Friendly and Highly Efficient Light‐Emission Ferroelectric Scintillators by Precise Molecular Design (Adv. Funct. Mater. 35/2021)

Ferroelectric Scintillators In article number 2102848, Li-Zhuang Chen, Yi Zhang, and co-workers present a series of metal halide compounds [RQ]2MnBr4 (R = H, methyl, ethyl, fluoroethyl, Q = quinuclidine). The precisely designed modulation towards cations not only arouses the satisfactory ferroelectricity of [FEtQ]2MnBr4, but also drastically enhances the photoluminescence quantum yield from 38.7% to 83.65%. [FEtQ]2MnBr4 is a promising candidate to achieve high scintillation performance compared with some commercial scintillators, such as bismuth germanium oxide and lutetium yttrium oxyorthosilicate.

COMPARATIVE CHARACTERISTICS OF COATINGS WITH SiO AND GeO ON LEUCOSAPPHIRE

The reasons for the sharp difference in the adhesion of multilayer coatings containing SiO or GeO together with Ge on a leucosapphire (Al2O3) plate have been established. It should be mentioned that Silicon(II) and Germanium(II) oxides are quite stable in the gaseous state and, contrary, are metastable in condensed state; at high temperature they disproportionate into ultra-dispersed composites of amorphous nature. A comparison is made of the surface properties of ultramicroscopic droplets formed on solid surfaces – a substrate or the previous layer – upon condensation of SiO, GeO, or Ge vapors on leucosapphire. A qualitative assessment of the ratio of the corresponding contact angles of wetting by the indicated melts, formed at the first moment of contact, has been carried out. In assessing the surface tension of SiO and GeO melts (or Si – SiO2 and Ge – GeO2 composites), we proceeded from the corresponding values for SiO2 and GeO2, which are 296 and 248 mJ/m2 near the crystallization temperatures. On this basis, it was established that the smallest value of the contact angle, and hence the best wetting, is observed for the GeO melt (somewhat less for the SiO melt) on the solid surface of Al2O3 or Ge; the solid surface of SiO or GeO (especially, the first of them) with molten germanium should be much weaker wetted. Hence, it follows that thin-film multilayer coatings obtained from Ge and GeO on a leucosapphire substrate should have a significantly higher climatic resistance due to higher adhesion compared to multilayer coatings from SiO and Ge. Indeed, a multilayer coating containing SiO on a leucosapphire substrate with a large surface can withstand storage in air for no more than 2–3 months and begins to peel off; at the same time, the GeO coating remains intact after 4 years of storage. Thus, the GeO film-forming material is a promising one for use in multilayer coatings such as cut-off filters in interference optics of the near and mid-IR spectral ranges.

Synthesis and Spectral Properties of Glasses in the System Bismuth Oxide – Germanium Oxide – Cerium Oxide

Synthesis and Spectral Properties of Glasses in the System Bismuth Oxide – Germanium Oxide – Cerium Oxide

On the Stability of the Optical Properties of an Antireflection Coating for Solar Cells Based on a Mixture of Germanium with Germanium Oxide

On the Stability of the Optical Properties of an Antireflection Coating for Solar Cells Based on a Mixture of Germanium with Germanium Oxide

Determination of Rare Impurities in High-Purity Germanium and Germanium Oxide by Inductively Coupled Plasma Atomic Emission Spectrometry

We have proposed a combination of techniques for quantitative chemical analysis of high-purity germanium and germanium oxide by inductively coupled plasma atomic emission spectrometry. The techniques are intended for determination of the rare-earth (RE) elements (except Pm), platinum group metals (PGMs) (except Os), I, S, Th, Tl, and U after acid dissolution of a sample (instrumental technique) and after separation of the matrix in the form of a highly volatile compound (combined technique). The instrumental technique allows all of the above elements to be determined. To take into account the effect of germanium on analytical signals of analytes, use is made of Be, Dy, or Gd internal standards. The best results in spike experiments have been obtained for the RE elements, PGMs, and I with the Be 234.861 nm; for Th, Tl, and U with the Dy 353.170 nm; and for S with no internal standards. The analyte detection limits (DLs) lie in the range n × 10–6 to n × 10–5 wt %. The combined technique is intended for lowering the DLs for Ir, Pd, Pt, Rh, Ru, S, Th, Tl, and U. Germanium was removed from weighed samples of germanium metal and germanium dioxide in the form of GeCl4 to above 99.99%. The analyte DLs were then from n × 10–7 to n × 10–6 wt %.

First principles study of Bi12GeO20: Electronic, optical and thermodynamic characterizations

Bismuth germanium oxide (Bi12GeO20) is one of the attractive members of sillenite compounds having fascinating photorefractive characteristics. The electronic, optical and thermodynamic properties of Bi12GeO20 were investigated using density functional theory (DFT) calculations. The experimental and calculated X-ray diffraction patterns were obtained as well-consistent with each other. The lattice constant of the cubic crystalline structure of Bi12GeO20 compound was calculated as 10.304 Å. The electronic band structure and partial density of states plots were reported and contribution of constituent atoms (Bi, Ge, O) to the valence and conduction bands was presented. The band gap energy of the Bi12GeO20 was calculated as 3.20 eV. This wide direct band gap energy provides Bi12GeO20 significant potential in ultraviolet applications. The spectra of real and imaginary components of dielectric function, refractive index, extinction coefficient and absorption coefficient were drawn in the 0−10 eV energy range. Temperature-dependent heat capacity plot indicated the Dulong-Petit limit as 825 J/mol.K. The results of the present study would present worthwhile information to device application areas of Bi12GeO20 compound.

High-rate and low-temperature performance of germanium nanowires anode for lithium-ion batteries

Abstract The original version of a negative electrode of lithium-ion battery is prepared. To this end the arrays of Ge nanowires were electrodeposited from an aqueous solution onto a titanium substrate with drop-like indium crystallization centers. The nanowires were characterized by SEM, TEM, EDX, XPS, galvanostatic cycling, CV, and EIS. Electrochemical tests were carried out in a wide temperature range with using the propylene-carbonate-based electrolyte. The electrochemical performances of the nanowires were shown to be dependent on the current density upon electrodeposition. The nanowires with diameter 20 to 40 nm and length up to 0.5 μm are covered with a thin oxide layer, consisting of both stoichiometric and non-stoichiometric germanium oxides. The electrodes demonstrate excellent features, namely room-temperature specific capacity ca. 1300 mAh g−1 at 1C and 4C rate, and about 850 mAh g−1 at 24C, as well as good low-temperature performance, 255 mAh g−1 at −50 °C.

Optical fibre with an offset core for SBS suppression

To raise the stimulated Brillouin scattering (SBS) threshold, we have fabricated an optical fibre having a core heavily doped with germanium oxide and displaced from the fibre axis. A method has been proposed for broadening the SBS gain spectrum of the fibre by winding it onto a small-diameter spool, and a broadening of the spectrum by 5.4 dB has been demonstrated, which indicates an increase in SBS threshold by 4.1 dB.

Nanostructured metal oxide@carbon dots through sequential chitosan templating and carbonisation route

Pyrolytic conversion of biomass stands as one of the most promising sustainable routes to carbon-based nanostructures, including carbon dots (CDs). Yet, molecular composition of functionalized carbon dots is limited to heteroatom doping and the incorporation of few single metal precursors. Besides, most of these modifications were undertaken by strenuous post-grafting procedures, requiring organic solvents for carbon dispersion and excluding a large library of potential reactants because of incompatible experimental conditions. In a significant divergence from the well-established literature, we herein disclose an innovative and highly versatile approach for enriching carbon dot functionalities. This straightforward method merges chitosan as carbon precursor and metal alkoxide as ceramic precursor and explores a twin growth of two dissimilar "metal oxide@carbon dots" phases through hydrothermal conversion of the carbohydrate solution. Owing to the structure-directing effect of chitosan toward metal alkoxide precursors, a set of crystalline metal oxides including titanium dioxide, germanium oxide, and iron oxide clusters were intimately fused within the in situ formed nitrogen-containing carbon framework. Distinctively, the following approach uses water as solvent and renewable biomass as carbon source and is expected to shed light on the hidden talent of discarded bio-waste for engineering functional nanomaterials.

Intercalation of germanium oxide beneath large-area and high-quality epitaxial graphene on Ir(111) substrate* *Project supported by the National Key Research & Development Program of China (Grant Nos. 2019YFA0308500, 2016YFA0202300, and 2018YFA0305800), the National Natural Science Foundation of China (Grant Nos. 61888102, 61925111, and 21661132006), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos. XDB30000000 and XDB28000000), and

Epitaxial growth on transition metal surfaces is an effective way to prepare large-area and high-quality graphene. However, the strong interaction between graphene and metal substrates suppresses the intrinsic excellent properties of graphene and the conductive metal substrates also hinder its applications in electronics. Here we demonstrate the decoupling of graphene from metal substrates by germanium oxide intercalation. Germanium is firstly intercalated into the interface between graphene and Ir(111) substrate. Then oxygen is subsequently intercalated, leading to the formation of a GeO x layer, which is confirmed by x-ray photoelectron spectroscopy. Low-energy electron diffraction and scanning tunneling microscopy studies show intact carbon lattice of graphene after the GeO x intercalation. Raman characterizations reveal that the intercalated layer effectively decouples graphene from the Ir substrate. The transport measurements demonstrate that the GeO x layer can act as a tunneling barrier in the fabricated large-area high-quality vertical graphene/GeO x /Ir heterostructure.

The Photoinitiators Used in Resin Based Dental Composite-A Review and Future Perspectives.

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin.

Shape control of cathodized germanium oxide nanoparticles

In this paper, hexagonal germanium dioxide (GeO2) nanostructures with different morphologies and sizes were successfully synthesized by a simple and fast electrodeposition method. We investigated the electrochemical growth mechanism and the structural and optical properties of the products through Fourier transform infrared spectroscopy (FTIR), dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and cathodoluminescence (CL). The results reveal that the electrodeposited GeO2 nanostructures are pure, dense, and highly crystalline. The XRD analyses indicate that the resulting GeO2 crystals only show peaks related to the α-quartz structure. CL measurements exhibit strong blue and green light emissions related to oxygen vacancies in the core of the GeO2 crystals. The resulting nanostructures may have potential application in integrated optical devices in the future.

Vibrational and optical identification of GeO2 and GeO single layers: a first-principles study.

In the present work, the identification of two hexagonal phases of germanium oxides (namely GeO2 and GeO) through the vibrational and optical properties is reported using density functional theory calculations. While structural optimizations show that single-layer GeO2 and GeO crystallize in 1T and buckled phases, phonon band dispersions reveal the dynamical stability of each structure. First-order off-resonant Raman spectral predictions demonstrate that each free-standing single-layer possesses characteristic peaks that are representative for the identification of the germanium oxide phase. On the other hand, electronic band dispersion analysis shows the insulating and large-gap semiconducting nature of single-layer GeO2 and GeO, respectively. Moreover, optical absorption, reflectance, and transmittance spectra obtained by means of G0W0-BSE calculations reveal the existence of tightly bound excitons in each phase, displaying strong optical absorption. Furthermore, the excitonic gaps are found to be at deep UV and visible portions of the spectrum, for GeO2 and GeO crystals, with energies of 6.24 and 3.10 eV, respectively. In addition, at the prominent excitonic resonances, single-layers display high reflectivity with a zero transmittance, which is another indication of the strong light-matter interaction inside the crystal medium.

Germanium Oxide Negative Electrodes - Tuning Synthesis Conditions Towards High-Energy and High-Power Lithium-Ion Cells

The transportation sector is continuously transitioning from combustion engines towards fully electric vehicles and lithium-ion batteries (LIBs) are the energy storage device of choice due to their high volumetric and gravimetric energy density.1 However, to meet future targets in terms of driving range and re-/charging times, the state-of-the-art graphite anode graphite needs to be replaced with materials offering even higher energy densities and, especially, better power capabilities.2 Alloying metal-oxides such as ZnO and SnO2 have been widely studied, since they offer high theoretical specific capacities (988 mAh g-1 and 1494 mAh g-1, respectively), while being environmentally friendly and non-toxic. Furthermore, such alloying metal oxides have high densities, which promises higher volumetric capacities compared to graphite. However, these high densities, in combination with the high overall Li+ uptake, result in pronounced volume expansion upon cycling. Furthermore, the eventually irreversible Li2O formation limits the practically achievable specific capacities to the alloying contribution only. It has been shown that this limitation can be overcome by introducing a transition metal (e.g., Fe, Co) into the lattice, leading to a reversible Li2O formation and favorable de-/lithiation kinetics.3,4 This concept of transition metal doping has recently also been transferred to germanium oxide – another example for a Li+ alloying oxide with an even higher theoretical specific capacity (i.e., 2152 mAh g-1) - and was shown to partially enable re-oxidation of germanium to germanium oxide, though (so far) only for the initial cycles.5 Within this study, we tackled the problem from a more comprehensive perspective and elaborate on the effect of different synthesis conditions, the introduction of Fe into GeO2, as well as the impact of different germanium oxide phases on the electrochemical performance. The latter aspect is, indeed, commonly overlooked so far when studying metal oxide anodes. The highly complementary techniques employed include, amongst others, in situ/operando characterization methods such as in situ high temperature XRD, operando XRD and operando dilatometry. Ultimately, we realized lithium-ion cells comprising lithium-rich Li1.2Mn0.6Ni0.2O2 cathodes with a specific energy of about 400 Wh kg-1 and stable cycling for more than 350 cycles. N. Nitta, F. Wu, J. T. Lee, and G. Yushin, Mater. Today, 18, 252–264 (2015).J. Asenbauer et al., Sustain. Energy Fuels (2020).D. Bresser et al., Chem. Mater., 25, 4977–4985 (2013).Y. Ma et al., Sustain. Energy Fuels, 2, 2601–2608 (2018).J. Wu, N. Luo, S. Huang, W. Yang, and M. Wei, J. Mater. Chem. A, 7, 4574–4580 (2019).

On the Optical Response of Tellurium Activated Zinc Selenide ZnSe:Te Single Crystal

In this study, the light output of a zinc selenide activated with tellurium (ZnSe: Te) single crystal was measured for X-ray radiography applications. A cubic crystal (10 × 10 × 10 mm) was irradiated using X-rays with tube voltages from 50 to 130 kV. The resulting energy absorption efficiency, detective quantum efficiency, and absolute luminescence efficiency were compared to published data for equally sized GSO: Ce (gadolinium orthosilicate) and BGO (bismuth germanium oxide) crystals. The emitted light was examined to estimate the spectral compatibility with widely used optical sensors. Energy absorption efficiency and detective quantum efficiency of ZnSe: Te and BGO were found to be similar, within the X-ray energies in question. Light output of all three crystals showed a tendency to increase with increasing X-ray tube voltage, but ZnSe: Te stood at least 2 EU higher than the others. ZnSe: Te can be coupled effectively with certain complementary metal–oxide–semiconductors (CMOS), photocathodes, and charge-coupled-devices (CCD), as the effective luminescence efficiency results assert. These properties render the material suitable for various imaging applications, dual-energy arrays included.

Reduction of interface state density in coaxial TiO2/Ge nanowire assembly-based heterostructure and superior photodetection

This paper compares the advantages of a catalyst-free vertically aligned coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) heterostructure compared to basic germanium nanowire (Ge-NW) on silicon (Si) substrate. Both were fabricated using the glancing angle deposition (GLAD) technique integrated into an electron beam evaporation system. The study is focussed on the successful suppression of native germanium oxide (GeO2) as well as the reduction of interface state density (Dit) by incorporating TiO2-NW. X-ray diffraction (XRD) patterns confirm the successful growth of rutile phase TiO2-NW in the coaxial TiO2-NW/Ge-NW assembly at room temperature. The crystal size analysis was carried out using the Scherrer equation and it confirmed the decrease in crystal size of GeO2 in the coaxial TiO2-NW/Ge-NW assembly. FEGSEM reveals the growth of vertically oriented NWs. Capacitance and conduction voltage data were used to extract the interface state density (Dit). The presence of TiO2 reduced the interface defect in the TiO2-NW/Ge-NW heterostructure compared to the bare Ge-NW sample. The optical absorption study showed that TiO2-NW/Ge-NW samples exhibited enhancement in the UV region primarily due to the presence of TiO2. The electrical characterization of Ag/TiO2-NW/Ge-NW/Si and Ag/Ge-NW/Si revealed a low dark current of −1.056 × 10−7 A/cm2 for Ag/TiO2-NW/Ge-NW/Si compared to −8.39 × 10−7 A/cm2 for Ag/Ge-NW/Si. Ag/TiO2-NW/Ge-NW/Si exhibited a superior rectification ratio, increased detectivity, and enhanced noise equivalent power compared to the Ag/Ge-NW/Si device. The TiO2-NW/Ge-NW heterostructure exhibited a fast temporal response with rise and fall times of ∼0.047 s and ∼0.037 s, respectively.

Influence of Al2O3 on the photoluminescence and optical gain performance of Nd3+ doped germanate and tellurite glasses

Abstract We investigated the influence of aluminum oxide, Al2O3, on the photoluminescence (PL) spectrum and optical gain (at 1064 m) of neodymium ion, Nd3+, doped tellurium and germanium oxide glasses with compositions TeO2 − ZnO and GeO2 − PbO, respectively. The PL properties of both materials were studied using a continuous-wave diode laser operating at 808 nm, in resonance with the Nd3+ transition 4I9/2 → 4F5/2. For samples containing Al2O3 it was observed PL intensity growth up to 30% in comparison with the samples without Al2O3. Luminescence decay (τm) from the 4F3/2 level was measured monitoring the 4F/32 → 4I11/2 transition. From calculations of the Judd–Ofelt parameters, the radiative lifetimes, the emission cross -section (σem) and the quantum efficiency of 4F3/2 → 4I11/2 transition were determined; the effective linewidth (Δλeff) was calculated to determine the gain bandwidth product (σem x Δeff), figure of merit (σem x τm) and saturation intensity (Is) parameters. Optical gain measurements were performed using a pump laser at 808 nm and a probe laser at 1064 nm. For the samples with Al2O3 the relative gain at 1064 nm reached ≈ 2.8 dB/cm (pump laser power: 400 mW) indicating an enhancement of about 65% for TeO2 − ZnO and 120% for GeO2 − PbO with respect to the samples without Al2O3. The optical gain enhancement is correlated to the PL intensity behavior and increases due to the presence of Al2O3 because the coordination environment of the Nd3+ changes and become more asymmetric leading to the growth of the emission cross-section. The present study shows that Nd3+ doped tellurium and germanium oxide glasses containing Al2O3 present particularly good prospects to be used as optical amplifiers at 1064 nm.

Correction method for the readout saturation of the DAMPE calorimeter

The DArk Matter Particle Explorer (DAMPE) is a space-borne high energy cosmic-ray and γ-ray detector which operates smoothly since the launch on December 17, 2015. The bismuth germanium oxide (BGO) calorimeter is one of the key sub-detectors of DAMPE used for energy measurement and electron–proton identification. For events with total energy deposit higher than decades of TeV, the readouts of PMTs coupled on the BGO crystals would become saturated, which results in an underestimation of the energy measurement. Based on detailed simulations, we develop a correction method for the saturation effect according to the shower development topologies and energies measured by neighbouring BGO crystals. The verification with simulated and on-orbit events shows that this method can well reconstruct the energy deposit in the saturated BGO crystal.

Thermal conductivity of rutile germanium dioxide

Power electronics seek to improve power conversion of devices by utilizing materials with a wide bandgap, high carrier mobility, and high thermal conductivity. Due to its wide bandgap of 4.5 eV, β-Ga2O3 has received much attention for high-voltage electronic device research. However, it suffers from inefficient thermal conduction that originates from its low-symmetry crystal structure. Rutile germanium oxide (r-GeO2) has been identified as an alternative ultra-wide-bandgap (4.68 eV) semiconductor with a predicted high electron mobility and ambipolar dopability; however, its thermal conductivity is unknown. Here, we characterize the thermal conductivity of r-GeO2 as a function of temperature by first-principles calculations, experimental synthesis, and thermal characterization. The calculations predict an anisotropic phonon-limited thermal conductivity for r-GeO2 of 37 W m−1 K−1 along the a direction and 58 W m−1 K−1 along the c direction at 300 K where the phonon-limited thermal conductivity predominantly occurs via the acoustic modes. Experimentally, we measured a value of 51 W m−1 K−1 at 300 K for hot-pressed, polycrystalline r-GeO2 pellets. The measured value is close to our directionally averaged theoretical value, and the temperature dependence of ∼1/T is also consistent with our theory prediction, indicating that thermal transport in our r-GeO2 samples at room temperature and above is governed by phonon scattering. Our results reveal that high-symmetry UWBG materials, such as r-GeO2, may be the key to efficient power electronics.

Recovery of pure germanium oxide from Zener diodes using a recyclable ionic liquid Cyphos IL 104

A novel process is developed for the recovery of germanium from the leach liquor of Zener diodes using solvent extraction. Extraction is carried out using a phosphonium ionic liquid, Cyphos IL 104, as an extractant. Preliminary investigations carried out on Ge(IV) extraction using Cyphos IL 104 include influence of various parameters like temperature, equilibration time, and concentration of extractant, chloride ion, and acid on the distribution of Ge(IV). NMR spectrum of Ge(IV)-extractant complex was analyzed to support the proposed extracting species of germanium. Quantitative extraction of germanium is achieved from 7 mol/L HCl onwards using 0.1 mol/L Cyphos IL 104. Optimum conditions for quantitative extraction of Ge from leach liquor of Zener diodes were developed. McCabe-Thiele plots were constructed for the extraction and stripping of Ge(IV) from leach liquor to determine the number of stages required at a particular aqueous/organic phase ratio. Separation of germanium from copper, mercury and iron has been achieved by selective stripping of these metal ions. Germanium is recovered as germanium oxide from the strip solution using NaOH as a precipitating agent. The synthesized germanium oxide is characterized by XRD, FE-SEM and EDX techniques.