Germanium Dioxide Research Articles

Analysis of high-purity germanium dioxide by ETV-ICP-AES with preliminary concentration of trace elements

The paper presents a combined technique of germanium dioxide analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) with preconcentration of trace elements by distilling off matrix and electrothermal (ETV) introduction of the trace elements concentrate into the ICP. Evaluation of metrological characteristics of the developed technique of high-purity germanium dioxide analysis was performed. The limits of detection (LODs) for 25 trace elements ranged from 0.05 to 20ng/g. The accuracy of proposed technique is confirmed by “added-found” («or spiking») experiment and comparing the results of ETV-ICP-AES and ICP-AES analysis of high purity germanium dioxide samples.

Controllable growth of stable germanium dioxide ultra-thin layer by means of capacitively driven radio frequency discharge

It is well recognized that native oxide of germanium is hygroscopic and water soluble, while germanium dioxide is thermally unstable and it is converted to volatile germanium oxide at approximately 400°C. Different techniques, implementing quite complicated plasma setups, gas mixtures and substrate heating, have been used in order to grow a stable germanium oxide. In the present work a traditional “RF diode” is used for germanium oxidation by cold plasma. Following growth, X-ray photoelectron spectroscopy demonstrates that traditional capacitively driven radio frequency discharges, using molecular oxygen as sole feedstock gas, provide the possibility of germanium dioxide layer growth in a fully reproducible and controllable manner. Post treatment ex-situ analyses on day-scale periods disclose the stability of germanium oxide at room ambient conditions, offering thus the ability to grow (ex-situ) ultra-thin high-k dielectrics on top of germanium oxide layers. Atomic force microscopy excludes any morphological modification in respect to the bare germanium surface. These results suggest a simple method for a controllable and stable germanium oxide growth, and contribute to the challenge to switch to high-k dielectrics as gate insulators for high-performance metal-oxide-semiconductor field-effect transistors and to exploit in large scale the superior properties of germanium as an alternative channel material in future technology nodes.

A New Strategy for Achieving a High Performance Anode for Lithium Ion Batteries—Encapsulating Germanium Nanoparticles in Carbon Nanoboxes

A novel strategy to improve the electrochemical performance of a germanium anode is proposed via encapsulating germanium nanoparticles in carbon nanoboxes by carbon coating the precursor, germanium dioxide cubes, and then subjecting them to a reduction treatment. The complete and robust carbon boxes are shown to not only provide extra void space for the expansion of germanium nanoparticles after lithium insertion but also offer a large reactive area and reduced distance for the lithium diffusion. Furthermore, the thus‐obtained composite, composed of densely stacked carbon nanoboxes encapsulating germanium nanoparticles (germanium@carbon cubes (Ge@CC)), exhibits a high tap density and improved electronic conductivity. Compared to carbon‐coated germanium bulks, the Ge@CC material shows excellent electrochemical properties in terms of both rate capability and cycling stability, due to the unique cubic core–shell structure and the effective carbon coating, so that the Ge@CC electrode delivers ≈497 mA h g−1 at a current rate of 30 C and shows excellent cycling stability of 1065.2 mA h g−1 at 0.5 C for over 500 cycles.

Dissolution of Germanium in Sulfuric Acid Based Solutions

The phenomenon and mechanism of germanium (hereinafter Ge) dissolution in sulfuric acid based solutions were studied. The sulfuric acid concentration, the presence of an oxidizer and the treatment time were varied as parameters of these tests. It was clarified that Ge surface is covered by two layers: germanium dioxide (hereinafter GeO2) and germanium monoxide (hereinafter GeO). GeO2 dissolves easily in water and in the sulfuric acid solutions with high water fraction. On the other hand, the dissolution of GeO and Ge is influenced strongly by the sulfuric acid concentration in the solution and the treatment time when oxidizer is present in the solution.

Facile synthesis of GeO2 nanostructures and measurement of photocatalytic, photovoltaic and photoluminescence properties

In this work, germanium dioxide nanostructures were prepared by a facile co-precipitation method. In this synthesis approach was used from acetyl acetone as capping agent to get the smallest nanoparticles. Some of effective parameters were optimized to achieve the best morphology of product, such as mole ratio of acetyl acetone, temperature and time. Small germania nanostructures with a size about 70 nm sizes were achieved in this method. Nanostructures were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared techniques X-ray energy dispersive spectroscopy and ultraviolet spectroscopy (UV–Vis). Various properties such as photoluminescence, photocatalytic and photovoltaic property were studied for as-prepared nanostructures. Results of germania nanostructures show that product revealed a PL band that caused from recombination of electron and hole in nanostructure. On the other hand, these nanostructures show a good photocatalytic behavior for degradation of methyl orange in presence of UV light. Therefore germania nanoparticles applied in photovoltaic measurement.

Optimising the settlement and hatchery culture of Saccharina latissima (Phaeophyta) by manipulation of growth medium and substrate surface condition

The phaeophyte macroalga Saccharina latissima is gaining economic importance as an aquaculture crop. To decrease costs associated with the hatchery, the time required for meiospores to develop into sporophytes ready for outplanting must be minimised and survivorship maximised. The settlement and juvenile development of S. latissima was examined in a series of experimental manipulations. It was determined that (1) Meiospore settlement should be conducted in the dark in nutrient-enriched medium. (2) Continued nutrient enrichment in the hatchery increased growth and survival of the developing sporophytes. (3) It is best to use the diatom inhibitor germanium dioxide only during settlement and the first week of light exposure, rather than continuously or not at all. This treatment leads to the highest survival rate and sporophyte length. (4) Pre-treating the settlement surface with a commercial yeast extract can increase settlement and early development size; however, over-application can be highly detrimental leading to reduced survival, size and patchy growth.

Improved Structural and Electric Characterstics of Al/ALD-HfO2/Ge MOS Capacitor by Germanium Dioxide and Germanium Oxynitride as Interfacial Layer

In this work HfO2 thin films has been deposited on Ge substrate by ALD with thickness of 9.77 nm. Thickness evaluation of film was done by Spectroscopic Ellipsometer (SE) and Filmetrics Reflectometer whereas chemical compositions and the states of the elements of the films were investigated by X-ray Photoelectron Spectroscopy (XPS). High-frequency Capacitance-Voltage (C-V), Conductance-Voltage (G-V) techniques and Current-Voltage (I-V) measurement were used to obtain the electrical properties of the high-k MOS capacitor. Different Ge surface cleaning methods preceding high-k ALD have been used for reducing oxide traps. Rapid Thermal Oxidation (RTO) and Rapid Thermal Nitridation (RTN) have been used to form the gate interlayer (IL) of GeO2 and GeON for the gate stack of P-MOS capacitor. By assimilating a thin GeON interlayer, excellent MOS capacitors with very small capacitance–voltage hysteresis and low gate leakage have been demonstrated. Physical and Electrical characterization investigates the quality of the oxynitride interlayer and low interface trap density (Dit ≈ 0.63×1012eV-1cm-2) in case of GeON/Ge which is improved as compared to the GeO2/Ge interface (Dit ≈ 2.53×1013 eV-1cm-2). Further electrical characterizations of HfO2 gate dielectric MOS capacitors deposited by the ALD using RTO & RTN as IL were investigated for the measurement of EOT and Qeff. The calculated EOT and Qeff values for GeON/Ge are 3.23 nm and 16.92×1012 cm-2 respectively which is better in comparison with GeO2 and as deposited samples.

Improved Structural and Electric Characterstics of Al/ALD-HfO2/Ge MOS Capacitor by Germanium Dioxide and Germanium Oxynitride as Interfacial Layer

A 9.77 nm HfO2 thin film has been deposited on Ge substrate by ALD method. Rapid Thermal Oxidation (RTO) and Rapid Thermal Nitridation (RTN) have been used to form the gate interlayers (ILs) of GeO2 and GeON between them. High-frequency Capacitance-Voltage (C-V), Conductance-Voltage (G-V) techniques and Current-Voltage (I-V) measurement were used to obtain the electrical properties of the high-k MOS capacitor. By assimilating a thin GeON interlayer, excellent MOS capacitors with very small capacitance–voltage hysteresis and low gate leakage have been demonstrated. The results suggest that the physical and electrical properties (K, Dit, Qeff, etc) improved by rapid thermal annealing (RTA) in nitrogen ambient, which improves the interface properties of HfO2/Si due to the densification of HfO2 thin films. We found that the GeON/Ge gate stack exhibit a reduced equivalent oxide thickness (3.23 nm), interfacial trap density, effective oxide charges (Qeff), C–V hysteresis and leakage current.

Origin of photocatalytic activity of nitrogen-doped germanium dioxide under visible light from first principles

The large intrinsic band gap of GeO2 hinders its potential application as a photocatalyst under visible-light irradiation. Here, we perform first-principles calculations to investigate the origin of the experimentally observed visible-light photocatalytic activity of GeO2 induced by N doping. Four possible defects (N-doping, N+H codoping, Ge vacancy and O vacancy) for the redshift of N-doped GeO2 are tentatively put forward. The lowest formation energy indicates that N+H codoped GeO2 is the most stable and easiest to form. N-doping at an oxygen site induces gap states, which are made up primarily of N 2p-derived states with some O 2p contributions, and the lowest-energy empty states is in the middle of the gap. For Ge vacancy model, O 2p states form the intermediate band, while Ge 4s orbitals localized in the gap contribute to the impurity level in O vacancy model. These gap levels lead to a reduced effective band gap, which is one of the potential interest for photocatalytic applications. Electronic transitions from these localized states induce a redshift to the visible region of the optical absorption edge. The calculated optical properties for N-doped GeO2 show a significant visible light absorption at about 400–600nm, in close agreement with the experimental result. This work indicates that N-doped GeO2 would be a promising photocatalyst with favorable photocatalytic activity in the visible region.

Nitrogen-doped carbon nanofibers with effectively encapsulated GeO2nanocrystals for highly reversible lithium storage

Germanium dioxide is a promising high-capacity anode material for lithium-ion batteries, but it usually exhibits poor cycling stability due to its large volume change during the lithiation/delithiation process.

Zn Doping of the Strontium Germanate and Photocatalytic Degradation of Gentian Violet

Zn doped strontium germanate has been prepared by the hydrothermal method using strontium acetate, germanium dioxide and zinc acetate as the raw materials. The Zn doped strontium germanate were analyzed by X-ray diffraction, scanning electron microscopy and solid UV-vis diffuse reflectance spectrum. The structures of Zn doped strontium germanate were confirmed to be hexagonal SrGeO3 and rhombohedral ZnGeO3 phases. The band gap of Zn doped strontium germante decreases from 3.67 eV to 2.88 eV with the change of the Zn doping mass percentage. The photocatalytic activity of the Zn doped strontium germanate has been evaluated for the photocatalytic degradation of gentian violet under UV light irradiation. The results reveal that the Zn doped strontium germanate has the enhanced photocatalytic activity. [DOI: 10.1380/ejssnt.2015.8]

Vibrational dynamics of rutile-type GeO2 from micro-Raman spectroscopy experiments and first-principles calculations

The vibrational dynamics of germanium dioxide in the rutile structure has been investigated by using polarized micro-Raman scattering spectroscopy coupled with first-principles calculations. Raman spectra were carried out in backscattering geometry at room temperature from micro-crystalline samples either unoriented or oriented by means of a micromanipulator, which enabled successful detection and identification of all the Raman active modes expected on the basis of the group theory. In particular, the Eg mode, incorrectly assigned or not detected in the literature, has been definitively observed by us and unambiguously identified at under excitation by certain laser lines, thus revealing an unusual resonance phenomenon. First-principles calculations within the framework of the density functional theory allow quantifying both wave number and intensity of the Raman vibrational spectra. The excellent agreement between calculated and experimental data corroborates the reliability of our findings.

Ca3ZnGeO2[Ge4O12]: a Ca-Zn germanate related to the mineral taikanite.

The title compound, Ca3ZnGeO2[Ge4O12] (tricalcium zinc germanium dioxide dodecaoxidotetragermanate), adopts a taikanite-type structure. The tetrahedral [Ge4O12] chain geometry is very similar to that of the silicate chain of taikanite, i.e. BaSr2Mn(3+)2O2[Si4O12], while the major difference is found parallel to the c axis. In taikanite, Mn(3+) octahedra form an infinite zigzag chain, whereas the title compound has a chain of distorted ZnO6 octahedra, which alternates with distorted GeO4 tetrahedra connected to each other via two common edges. Eightfold-coordinated Ca(2+) polyhedra and ZnO6 octahedra form a slab parallel to (001) which alternates with another slab containing the tetrahedrally coordinated Ge sites along the c axis.

Electrodeposited Germanium On Silicon Substrate Using A Mixture Of Germanium Tetrachloride And Propylene Glycol

We report the deposition of germanium (Ge) film on silicon (Si) substrate by a simple and low cost electrochemical deposition using a mixture of germanium tetrachloride (GeCl4) and propylene glycol (C3H8O2). The effects of deposition environment and applied current density on the properties of deposited Ge films were investigated. Ge film containing germanium dioxide (GeO2) microclusters was obtained for deposition in air-exposed environment while high purity Ge film with no impurity detectable by energy-dispersive x-ray spectroscopy (EDS) was obtained in nitrogen (N2) filled environment. In Raman spectra, N2 exposed sample shows smaller full width at half maximum (FWHM) values of Ge-Ge peak compared to air exposed sample, thereby indicating better crystallinity of Ge. Relatively flat and smooth Ge surfaces with the average roughnesses of 0.828-1.069 nm were obtained for all tested current densities of 10, 20 and 60 mAcm-2. The mean Ge crystallite grain sizes were determined to be in the range of 2-4 nm. In qualitative voltammetry study, two reduction peaks were observed in cyclic voltammograms measurement which confirms that the deposition of Ge at cathode occurs via two reduction processes. It is expected that the impurity-free Ge film on Si is promising for various device application towards heterogeneous integration on Si platform.

Analysis of high-purity germanium dioxide by atomic absorption spectrometry

To ensure analytical support for the growth of bismuth orthogermanate single crystals, we have developed an electrothermal atomic absorption technique for analysis of germanium dioxide with the separation of the host through reactive evaporation in the form of germanium tetrachloride. The technique allows Cd, Co, Cu, Cr, Mn, Ni, and Pb to be determined with detection limits in the range 1 × 10−8 to 1 × 10−8 wt %.

Structural and thermodynamic consideration of metal oxide doped GeO2 for gate stack formation on germanium

A systematic investigation was carried out on the material and electrical properties of metal oxide doped germanium dioxide (M-GeO2) on Ge. We propose two criteria on the selection of desirable M-GeO2 for gate stack formation on Ge. First, metal oxides with larger cation radii show stronger ability in modifying GeO2 network, benefiting the thermal stability and water resistance in M-GeO2/Ge stacks. Second, metal oxides with a positive Gibbs free energy for germanidation are required for good interface properties of M-GeO2/Ge stacks in terms of preventing the Ge-M metallic bond formation. Aggressive equivalent oxide thickness scaling to 0.5 nm is also demonstrated based on these understandings.

Pressure-induced structural transition in amorphous GeO2: a molecular dynamics simulation

We studied the structural and dynamical properties of amorphous germanium dioxide (GeO2) from low to high pressure by means of the classical molecular dynamics technique. The simulations were done in the micro-canonical ensemble, with systems at densities ranged from 3.16 to 6.79 g/cm3, using a pairwise potential. The network topology of the systems is analyzed at atomic level through partial pair correlations, coordination number and angular distributions. The dynamic properties were characterized by means of the vibrational density of states. According the density increases, a structural transformation from a short-range order, defined by a building block composed by a basic (GeO4) tetrahedron, to a basic (GeO6) octahedron is observed. The vibrational density of states also presents important changes when the density increases, with a low frequency band lessened, and a high density band wider and flatter.

Structural, elastic, and mechanical properties of germanium dioxide from first-principles calculations

The structural, elastic, and mechanical properties of the available experimental and theoretical phases of germanium dioxide (GeO2) are investigated. Germanium dioxide (GeO2) is an important material in science and technology due to its wide-ranging applications, and many researches have been proposed to investigate its crystalline polymorphs. Although many phases have been reported, the systematic analysis and comparison of various phases are still lacking. In our paper, the energy, structural, elastic, mechanical properties and mechanical stability of the available experimental and theoretical phases of GeO2 are investigated from first-principles within the density-functional theory (DFT) plus the local density approximation. The order of increasing ground-state energy is as follows: P42/mnm, Pnnm, P21/c, Pbcn, Pnma, P3221 (P3121), P41212, C2/c, P63/mmc, Pa3¯, P4/mcc, P6222, C2221, Pn3¯m and P6¯2m, indicating that tetragonal P42/mnm phase and hexagonal Fe2P-type P6¯2m phase have minimum and maximal ground-state energy, respectively. The structural parameters, elastic constants, bulk modulus, shear modulus, Young׳s modulus, Poisson׳s ratio, Lamé׳s constants as well as mechanical stability have been obtained and discussed, indicating that P6222 and P6¯2m phases are unstable under zero pressure. These results may help to understand GeO2 for future applications.

Oxidation kinetics of the germanium-alloyed AK7M2 + 0.05% Sr alloy

The oxidation kinetics of the germanium-alloyed AK7M2 + 0.05% Sr alloy in air at temperatures of 773 K, 798 K, and 823 K is investigated by the thermogravimetric method. It is revealed that the addition of germanium up to 0.6 wt % decreases the oxidation rate, as evidenced by an increase in the apparent activation energy of oxidation from 14.7 to 79.8 kJ/mol, which drops again to 25.2 kJ/mol as the Ge content increases to 1.0 wt %. The true oxidation rate varies in limits of (4.30–6.00) × 10−4 kg/(m2 s), depending on the amount of alloying component. Silicon dioxide SiO2 and germanium dioxide GeO2 are also revealed in oxidation products of alloys along with γ-Al2O3.

GeO2 influence on the formation of near-infrared emitting centers in Bi-doped multicomponent silicate glasses

A meaningful increase in the number of NIR emission centers was experimentally observed in bismuth-doped multicomponent silicate glasses additionally doped with germanium dioxide. The emission and excitation spectra of the glass sets were monitored and compared with the spectra of radiative oxygen-deficient centers in vitreous silica and germania.