Ge Accumulation Research Articles

Inversion of the Internal Electric Field due to Inhomogeneous Incorporation of Ge Dopants in GaN/AlN Heterostructures Studied by Off-Axis Electron Holography.

The engineering of the internal electric field inside III-nitride devices opens up interesting perspectives in terms of device design to boost the radiative efficiency, which is a pressing need in the ultraviolet and green-to-red spectral windows. In this context, it is of paramount importance to have access to a tool like off-axis electron holography which can accurately characterize the electrostatic potentials in semiconductor heterostructures with nanometer-scale resolution. Here, we investigate the distribution of the electrostatic potential and chemical composition in two 10-period AlN/GaN (20 nm/20 nm) multilayer samples, one of these being non-intentionally doped and the other with its GaN layers heavily doped with Ge at a nominal concentration ([Ge] = 2.0 ± 0.2 × 1021 cm-3) which is close to the solubility limit. The electron holography experiments demonstrate the effects of free carrier screening in the case of Ge doping. Furthermore, in the doped sample, an inversion of the internal electric field is observed in some of the AlN layers. A correlated study involving holography, electron dispersive X-ray spectroscopy, and theoretical calculations of the band diagram demonstrates that the perturbation of the potential can be attributed to Ge accumulation at the heterointerfaces, which paves the way to the use of Ge delta doping as a design tool to tune the electric fields in polar heterostructures.

Investigation of the temperature stability of germanium-rich SiGe layers on Si(111) substrates

In this work, we investigated fully relaxed SiGe and pure Ge layers on Si(111) substrates, regarding their temperature stability. The layers were annealed at various temperatures up to 650 °C directly after growth. The Ge content of the Si1−xGex layers was varied between 0.6 and 1. We investigated effects due to surface segregation of Ge in the SiGe layers. During heat treatment, different surface reconstructions were observed. The SiGe layers remained smooth with a root-mean square surface roughness below 0.5 nm up to temperatures of 500 °C and a 7 × 7 surface reconstruction was seen. Annealing at higher temperatures corresponding to a 7 × 7–“1 × 1” phase transition, the surface roughness increased to more than 2 nm and island formation was observed. We measured the in-plane lattice constant of the surface as a function of temperature and confirmed a strong effect of Ge segregation on the surface strain. The Ge accumulation at the surface was confirmed by angle-resolved X-ray photoelectron spectroscopy. The high adatom density of the “1 × 1” reconstruction in combination with compressive strain led to island nucleation when cooling down. Pure Ge layers remained smooth even after annealing up to 650 °C.

Meclofenamic Acid Restores Gefinitib Sensitivity by Downregulating Breast Cancer Resistance Protein and Multidrug Resistance Protein 7 via FTO/m6A-Demethylation/c-Myc in Non-Small Cell Lung Cancer.

Background and ObjectiveGefitinib (GE) is a first-line epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) for patients with advanced non-small cell lung cancer (NSCLC) carrying EGFR activating mutations. However, drug resistance limits the clinical efficacy of gefitinib and ultimately leads to extremely poor clinical benefit. Meclofenamic acid (MA) is a non-steroidal anti-inflammatory drug (NSAID) that relieves moderate and severe pain. In the present study, we aim to determine the MA sensibilization of GE in NSCLC.MethodsMTT assay was conducted to determine the synergistic effect of MA with GE in GE-sensitive and -resistant cell lines based on the Chou–Talalay method. The Annexin V-PI flow cytometry analysis was conducted to evaluate apoptosis. Western blot assay was used to detect alterations of EGFR downstream molecules. Tritium-labeled GE accumulation analysis was used to determine the efflux activity of GE. Dot blot assays were conducted to determine m6A levels after the MA and GE co-administration. Western blot evaluated the expression of FTO, c-Myc, MRP7, BCRP, and apoptotic proteins.ResultsMA showed a significant synergistic effect with GE in GE-resistant NSCLC cells; co-administration of MA with GE induced caspase-related apoptosis in resistant NSCLC cells. Moreover, EGFR downstream molecules, including Akt and MAPKs pathways, were significantly inhibited by the MA-GE combination. Short-term incubation of MA did not alter the efflux of GE; however, after incubation for 24 h, the accumulation of tritium-labeled GE significantly increased. A mechanism study showed that co-administration of MA and GE significantly downregulated BCRP and MRP7 expression in GE-resistant cells; increased N6-methylation was also observed after co-administration. The FTO/c-Myc was determined as target pathways on MA and GE co-administration mechanisms.ConclusionOur findings provide novel therapeutic approaches for GE-resistant NSCLC by combination use with MA through FTO-mediated N6-demethylation.

Secondary metabolites released by the rhizosphere bacteria Arthrobacter oxydans and Kocuria rosea enhance plant availability and soil–plant transfer of germanium (Ge) and rare earth elements (REEs)

Here, we explore effects of metallophore-producing rhizobacteria on the plant availability of germanium (Ge) and rare earth elements (REEs). Five isolates of the four species Rhodococcus erythropolis, Arthrobacter oxydans, Kocuria rosea and Chryseobacterium koreense were characterized regarding their production of element-chelators using genome-mining, LC-MS/MS analysis and solid CAS-assay. Additionally, a soil elution experiment was conducted in order to identify isolates that increase solubility of Ge and REEs in soil solution. A. oxydans ATW2 and K. rosea ATW4 released desferrioxamine-, bacillibactin- and surfactin-like compounds that mobilized Ge and REEs as well as P, Fe, Si and Ca in soil. Subsequently, oat, rapeseed and reed canary grass were cultivated on soil and sand and treated with cells and iron depleted culture supernatants of A. oxydans ATW2 and K. rosea ATW4. Inoculation increased plant yield and shoot phosphorus (P), manganese (Mn), Ge and REE concentrations. However, effects of the inoculation varied substantially between the growth substrates and plant species. On sand, A. oxydans ATW2 increased accumulation of REEs in all plant species and root–shoot translocation in rapeseed, while K. rosea ATW4 enhanced REE accumulation in rapeseed only, without effects on other plant species. Sand-cultured oat plants showed increased Ge accumulation and root–shoot translocation in presence of A. oxydans ATW2 cells and K. rosea ATW4 supernatant; however, there was no effect on other plant species, irrespective the growth substrate used. In contrast, soil-cultured rapeseed showed enhanced REE accumulation in presence of cells of A. oxydans ATW2 while there were no effects on other plant species and Ge. The processes involved are not yet fully understood. Nevertheless, we demonstrated that chemical microbe–soil–plant relationships influence plant availability of nutrients together with Ge and REEs, which has major implications on our understanding of biogeochemical element cycling and development of sustainable bioremediation and biomining technologies.

The origin, migration, and accumulation mechanism of germanium and the metallogenic model of coal-hosted Ge ore deposits in Wulantuga, Erlian Basin, China

To explore the source, migration, and enrichment mechanism of germanium (Ge) and the metallogenic model of the Wulantuga coal-hosted Ge ore deposits in the Shengli Coalfield, this study analyzed the geochemical parameters of Ge-rich coal seams, including major element, trace elements, and rare earth element (REE) compositions, with X-ray fluorescence (XRF) spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA). An isoline map of Ge concentration and a cross-section map of sedimentary strata and Ge element distribution were drawn with the sampling data. The results showed that there were three periods of Ge accumulation in the Wulantuga coal seam. The enrichment coefficients of the low-content Ge samples and high-content Ge samples displayed that Ge was enriched together with As, Mo, Sb, and W. Compared with the Ge-bearing parent rocks located southwest of the Wulantuga area, the Ge-rich samples are clearly enriched in heavy REEs relative to light REEs in the REE distribution pattern, with positive anomalies of Tb, Ho, Tm, (La/Yb)n and (La/Sm)n > 1, as well as a very high positive δEu anomaly, which indicated that the Ge ore deposit in Wulantuga was indeed likely affected by hydrothermal fluids with a left-slanting REE distribution pattern. In addition, based on the sulfophilic affinity and organic affinity of Ge and the geochemical characteristics of Ge in hydrothermal fluids, the authors speculate that the Ge-rich fluids originated from thermal convection and the interaction between surface freshwater carrying O2 and hydrothermal fluids from the mantle.

Effects of exogenous germanium and effective microorganisms on germanium accumulation and nutritional qualities of garlic (Allium sativum L.)

Organic germanium (Ge) compounds show vital beneficial effects for our health and are widely used as medical applications and dietary supplements. Inorganic Ge can be absorbed by plants and further accumulated and transformed into organic Ge compounds in plant tissues, which can be further consumed as Ge-rich foods. Meantime, the presence of Ge can improve the physiological functions of plants such as the salt tolerance and the peroxidase activities in leaves. Therefore, improving the Ge content of Ge-rich plants by fertilizing exogenous inorganic Ge is of important and an efficient way to obtain more organic germanium. Garlic is one of the natural Ge-rich plants and possesses prodigious medicinal and nutraceutical properties. The main edible parts of garlic include bulb, scape and seedling in China. However, the effects of exogenous Ge on the Ge accumulation and nutritional qualities of garlic are not apparent, and the suitable applying concentrations and frequencies are also poorly known. Here, using garlic cultivar G024 and GeO2 as exogenous Ge, two experiments were performed to reveal the effects of exogenous Ge on garlic. Besides, a third experiment that brings in the factor of effective microorganisms (EM) inoculation was also conducted to evaluate the combined effects of exogenous Ge and EM application on garlic seedlings. Results showed that foliar spraying 6–72 mg/L GeO2 solutions significantly affects the Ge accumulation and distribution in garlic plants; foliar spraying 9–12 mg/L GeO2 at the bolting period is appropriate for producing the Ge-rich garlic scapes and bulbs; soil supplying 100 mg GeO2 together with EM inoculation are suitable for obtaining Ge-rich garlic seedlings. The present study provided useful information for the field production of Ge-rich garlic.

Orlen lets contract for Lithuanian refinery

Organic germanium (Ge) compounds show vital beneficial effects for our health and are widely used as medical applications and dietary supplements. Inorganic Ge can be absorbed by plants and further accumulated and transformed into organic Ge compounds in plant tissues, which can be further consumed as Ge-rich foods. Meantime, the presence of Ge can improve the physiological functions of plants such as the salt tolerance and the peroxidase activities in leaves. Therefore, improving the Ge content of Ge-rich plants by fertilizing exogenous inorganic Ge is of important and an efficient way to obtain more organic germanium. Garlic is one of the natural Ge-rich plants and possesses prodigious medicinal and nutraceutical properties. The main edible parts of garlic include bulb, scape and seedling in China. However, the effects of exogenous Ge on the Ge accumulation and nutritional qualities of garlic are not apparent, and the suitable applying concentrations and frequencies are also poorly known. Here, using garlic cultivar G024 and GeO2 as exogenous Ge, two experiments were performed to reveal the effects of exogenous Ge on garlic. Besides, a third experiment that brings in the factor of effective microorganisms (EM) inoculation was also conducted to evaluate the combined effects of exogenous Ge and EM application on garlic seedlings. Results showed that foliar spraying 6–72 mg/L GeO2 solutions significantly affects the Ge accumulation and distribution in garlic plants; foliar spraying 9–12 mg/L GeO2 at the bolting period is appropriate for producing the Ge-rich garlic scapes and bulbs; soil supplying 100 mg GeO2 together with EM inoculation are suitable for obtaining Ge-rich garlic seedlings. The present study provided useful information for the field production of Ge-rich garlic.

Organic-association of Ge in the coal-hosted ore deposits: An experimental and theoretical approach

The Wulantuga and Lincang germanium deposits in China are both giant coal-hosted Ge deposits. It is a consensus that the enriched Ge in the high-Ge coals is predominantly associated with the organics, but the specific bonding sites for Ge still remain unclear. In the present study, conventional spectral analyses (13C NMR and KBr-FTIR) and the density functional theory (DFT) calculations were used to investigate the functional groups responsible for Ge accumulation in the Wulantuga and Lincang deposits.The analytical results of the semi-quantitative NMR and FTIR suggest that the phenolic hydroxyls suffered alteration by HCl-HF treatment and are most likely the bonding sites for Ge by comparing the structures of the micronized and acid demineralized huminites from two high-Ge coals. Five acidic hydroxyl containing model compounds (catechol, phenol, ethanol, acetic acid, and benzoic acid) were selected to investigate the binding nature of Ge-O complexes, and the results indicate that phenolic hydroxyls have higher reactivity relative to other groups due to the easier exposure of oxygen by hydrogen dissociation, which is the key step for the formation of Ge-O complexes. Both the experiment and calculation results support the significance of phenolic hydroxyls for Ge fixation in the two deposits, but the present study does not exclude the possible contribution of other O-containing groups.This study facilitates understanding the mode of occurrence of Ge in the high-Ge coals and revealing the mechanism of the organic association of Ge in the coal-hosted Ge ore deposits from the perspective of coal structure.

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.

Strain evolution of SiGe-on-insulator fabricated by germanium condensation method with over-oxidation

Strain evolutions of SiGe film during Ge condensation processes of SiGe on silicon-on-insulator were studied in detail with assistance of X-ray diffraction. At the beginning of Ge condensation, SiGe on silicon-on-insulator with low Ge fraction was oxidized at higher temperature of 1150°C, the strong plastic deformation of buried SiO2 and Si-Ge intermixing relieved most of the strain in SiGe with increasing Ge fraction. When temperature was reduced to 900°C for oxidation of SiGe layer with higher Ge fraction, Ge accumulation overmatched Si-Ge inter-diffusion, resulting in non-uniform profile of Ge in SiGe layer. During this period, plastic deformation of buried SiO2 can be neglected and dislocation gliding plays a significant role in relieving strain in SiGe, which enlarges the surface roughness. The strain in SiGe increases gradually with condensation time for the thickness of SiGe layer reduces close to its critical thickness, even with higher Ge fraction. Intensive over-oxidation of germanium-on-insulator materials was suggested to be effective to fully relax the compressive strain but should be precisely controlled to avoid surface deterioration.

Accumulation and Toxicity of Germanium in Cucumber under Different Types of Germaniums

The effects of germanium dioxide (GeO2) and 2-carboxyethyl germanium sesquioxide (Ge-132) treatments on cucumber (Cucumis sativus L.) growth and Ge accumulation and toxicity were investigated. Accumulated Ge contents in plant treated with GeO2 were two times greater than that in plants treated with Ge-132. Germanium accumulated primarily in the shoots in the GeO2 treatments and in the roots in the Ge-132 treatments. In contrast GeO2 was easily transported from roots to shoots. In cucumber fruit, the range of Ge content in both the GeO2 and Ge-132 treatments was in the order of stalk > rind > pulp > seeds, suggesting that Ge accumulation was based on distance from xylem. Silicon (Si) content significantly decreased as GeO2 concentration increased, but there was no difference in Si content in the Ge-132 treatment. Therefore, plant growth and Ge accumulation are affected differently by GeO2 and Ge-132 treatments, based partly on treatment concentrations.

Characterization of channel strain evolution upon the silicidation of recessed source/drain Si1−xGex structures

This letter reports on Ni germanosilicide formation on recessed Si0.82Ge0.18 source/drain structures and its effects on channel strain. A combination of transmission electron microscopy techniques, including nanobeam diffraction, shed some light on a previously unrecognized factor in the channel strain evolution during silicidation: a Ge accumulation layer produced at the bottom of the germanosilicide layer. The formation of such a Ge rich layer added an additional compressive strain to the channel strain upon moderate silicidation, while the contribution of thermal strain arising from the cooling cycle became dominant in an excessively silicided sample, which turned the channel strain into a tensile value.

Distinct silicon and germanium pathways in the soil‐plant system: Evidence from banana and horsetail

Plants strongly impact the continental silicon cycle by taking up Si and precipitating opal phytoliths which are recycled into the soil. Studying Ge incorporation, a chemical analog of Si, relative to Si may provide a useful tracer of Si pathways. However, Ge uptake and transport through plants and the impact on Ge/Si of phytoliths remain poorly understood. Here, we report Ge uptake and accumulation and Ge/Si fractionation in all plant parts and solutions from: (1) hydroponic banana, (2) in situ sampled banana, and (3) horsetails. We further combine these data with δ29Si from banana plants. Our data reconcile opposite conclusions drawn from previous studies on Ge uptake and pathways. No discrimination of Ge occurred at the root‐solution interface. Banana and horsetails were shown to accumulate Ge in roots: a previous study provided evidence of low Ge/Si ratios in root phytoliths which contrasts with high bulk Ge/Si ratios in roots we report here. This suggests that Ge is organically trapped in roots. Consequently, shoots display lower Ge/Si ratios, without fractionation between shoot parts since Ge would follow transpiration stream as silicon, and is not discriminated between shoot parts. This contrasts with the two‐step discrimination against heavy Si isotopes, at the root‐solution interface, and then within the shoots. The soil composition (clays versus Fe oxides) has a leading role on the Ge/Si signatures of plants which may in turn impact on the Si and Ge fluxes to the global ocean.

Fabrication of compositional graded Si1−xGex layers by using thermal oxidation

Compositional graded and highly relaxed Si1−xGex layers have been fabricated by using thermal oxidation at high temperature. It was found that the behavior of Ge atoms during thermal oxidation was significantly dependent of the oxidation temperature. The Ge accumulation below the oxide occurred at 800 and 900 °C due to a large difference of the heat formation of GeO2 and SiO2. However, Si1−xGex layers oxidized in 1000 °C did not show any Ge accumulation because Ge diffusion efficiently occurred. The compositional graded Si1−xGex layers fabricated by thermal oxidation can be used as virtual substrates for the strained-Si and relaxed-SiGe applications.

Nanometer-thick SGOI structures produced by Ge+ ion implantation of SiO2 films and subsequent hydrogen transfer of Si layers

Nanometer-thick silicon-germanium-on-insulator (SGOI) structures have been produced by the implantation of Ge+ ions into thermally grown SiO2 layer and subsequent hydrogen transfer of silicon film on the Ge+ ion implanted substrate. The intermediate nanometer-thick Ge layer has been formed as a result of the germanium atom segregation at the Si/SiO2 bonding interface during annealing at temperatures 800–1100оС. From a thermodynamic analysis of Si/Ge/SiO2 system, it has been suggested that the growth of the epitaxial Ge layer is provided by the formation of a molten layer at the Si/SiO2 interface due to the Ge accumulation. The effect of germanium on the hole mobility in modulation-doped heterostructures grown over the 3–20nm thick SGOI layers was studied. An increase in the Hall hole mobility in SGOI-based structures by a factor of 3–5 was obtained in comparison with that in respective Ge-free SOI structures.

Strain relaxation in SiGe layer during wet oxidation process

The strain relaxation in SiGe layer on silicon substrate during wet oxidation at 1000°C was investigated. It was proposed that the competition between Ge accumulation and diffusion led to different strain-relaxation behaviors. At the very beginning, Ge atoms at the oxidizing interface were quickly accumulated due to the high oxidation rate resulting in the additional nucleation of misfit dislocations (therefore a lot of threading dislocations) to relieve stress after the thickness of the Ge condensed layer was larger than the critical value. And then, when the Ge accumulation rate was less than the diffusion rate, Ge content started to decrease from a maximum value and the strain in the SiGe layer was mainly relieved through surface roughing and the degree of strain relaxation reached a maximum. When the samples were further oxidized, Ge accumulation could be neglected because of the self-limiting oxidation and the Ge diffusion dominated the consequent processes. As a result, Ge content at the interface was reduced, with the contribution of the strain relaxation in SiO2 viscously, leading to the decrease of degree of strain relaxation in the SiGe layers slowly.

Compositional analysis of Si nanostructures: SIMS–3D tomographic atom probe comparison

3D atom probe tomography (APT) is introduced as a powerful compositional and spatial analytical tool for SiGe nanostructures. Compositional analysis of SiGe structures demonstrates that the location and identity of Si, Ge and B atoms can be detected in three dimensions. Superior sensitivity at Si–SiGe–Si interfaces is specifically witnessed by both the quantification of Ge accumulation at an interface (14% by atom probe versus 9% by SIMS) and a slope roll-off of ∼1 nm/decade for atom probe compared to ∼7 nm/decade for the corresponding SIMS analysis. Additionally, APT provides chemical roughness measurements of buried interfaces. In a specific case, a Si–SiGe–Si interface had a measured roughness of 0.47 nm at the Si–SiGe leading edge and 0.26 nm at the SiGe–Si trailing edge.

High-Temperature Oxidation of Ti3GeC2 and Ti3Ge0.5Si0.5C2 in Air

In this paper, we report on the oxidation behavior of and . The oxidation kinetics were studied thermogravimetrically in air in the temperature range. The oxidation layers formed on at were protective; at and higher, they were not. The addition of Si to slightly enhanced its oxidation resistance, but at and above, the layers formed were again not protective. In both cases the oxidation occurred mostly by the inward diffusion of oxygen through a rutile-based solid solution with . At higher temperatures and/or longer times, Ge accumulation was observed at the oxide/carbide interface. At and higher, however, the oxygen induces the peritectic decomposition of into Ge and, presumably, a titanium oxycarbide. At , part of the Ge escapes to the surface and forms copious amounts of whiskers with hexagonal symmetry. In the temperature range explored there is no oxygen dissolution in the carbide matrices.

Probing the composition of Ge dots and Si∕Si1−xGex island superlattices

We use analytical transmission electron microscopy to map the composition of Ge dot and Si∕Si1−xGex island structures grown on (001) Si by molecular beam epitaxy or ultrahigh vacuum chemical vapor deposition. Energy-dispersive x-ray spectroscopy reveals that nominally pure Ge dots grown by molecular beam epitaxy at 650°C exhibit considerable intermixing with the average Ge composition typically increasing from nearly zero at the base to about 50% at the top of the dot. In pyramid shaped dots, the Ge composition increases linearly up to the top of the dot, while for dome dots, a saturation of the incorporation rate is seen beyond a distance of 7nm from the substrate interface. Probing of Si∕Si1−xGex island superlattices also reveals large Si∕Ge intermixing with a Ge accumulation at the crest and Ge depletion at the troughs of the islands. These results are corroborated by x-ray diffraction and Raman scattering measurements.

Germanium movement mechanism in SiGe-on-insulator fabricated by modified Ge condensation

The movement of Ge during Ge condensation in SiGe-on-insulator (SGOI) fabrication is studied based on the competition between the diffusion of Ge atoms and accumulation of Ge atoms. The diffusion of Ge atoms overwhelms the Ge accumulation at the top thermal oxide∕SiGe interface, resulting in a flat Ge profile in the SGOI layer. However, the opposite result is found at the bottom SiGe∕buried-oxide (BOX) interface. The Ge diffusion towards the BOX is blocked because of the much smaller diffusion coefficient of Ge in the BOX than that in the SiGe layer. The Ge accumulation effects are more dominant than the diffusion of Ge, and so Ge atoms pile up near the BOX giving rise to an abrupt profile. The disappearance of the SiGe lattice structure near the SiGe∕BOX interface is also found in the sample oxidized for a longer time due to the reduction of the melting point of SiGe alloys with higher Ge fractions.