High Ga Content Research Articles

Structural and optical properties of indium‐rich InGaN islands

AbstractIndium‐rich Inx Ga1‐x N islands (x ≥ 0.87) grown by metalorganic chemical vapor deposition at growth temperatures ranging from 550‐750 °C were investigated. With the increasing growth temperature, the InGaN dot size increases while the dot density decreases due to the enhanced surface migration of In/Ga adatoms at elevated temperatures. In addition, the composition of InGaN islands was also found to be varied with the growth temperature. At lower growth temperatures, a higher Ga content can be achieved due to the relatively lower migration ability of Ga adatoms. At higher growth temperatures, the deposited InGaN material tend to decompose into In‐rich islands and a thin Ga‐rich layer. Photoluminescence investigations show that these In‐rich islands exhibit a near‐infrared emission band. For samples grown at higher temperatures, a visible emission band was also observed. The visible emission band may arise from defect bands introduced during the formation of Ga‐rich InGaN layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Methanol-to-olefin over gallosilicate analogues of chabazite zeolite

Gallosilicate analogues of chabazite zeolite with CHA topology have been synthesized, characterized and employed as catalysts for the methanol-to-olefin (MTO) process. 71Ga NMR spectra indicate that Ga is incorporated into the framework of these zeolitic materials during the hydrothermal synthesis. IR measurements show that stretching vibration of the hydroxyl groups associated with the framework Ga appears at 3600 cm −1. The gallosilicates with high Ga contents show Lewis acidity, which is possibly caused by degalliation during calcination, whereas only Brönsted acid sites are observed on the sample with relatively low Ga content. The catalysts show promising catalytic performance in the MTO reaction, particularly from the stability point of view, compared with H[Al]CHA zeolites. This is attributed to the weak Brönsted acidity associated with the framework Ga in the gallosilicates.

An approach to the bulk textured Fe81Ga19 rods with large magnetostriction

Bulk textured Fe81Ga19 alloy with large magnetostiction of up to 830ppm is fabricated using the technique of rapid directional solidification by triggering the undercooled Fe81Ga19 melts. The saturation magnetostriction is about two times as large as the maximum of the earlier report on Fe–Ga bulk samples. The large magnetostriction is ascribed to the high concentration of Ga–Ga atom pairs created by rapid solidification and their preferential orientation in the [100] textured rod.

Investigation of Optical Nonlinearities and Carrier Dynamics in In-Rich InGaN Alloys

We present experimental studies of nonequilibrium carrier dynamics in InGaN alloys with 70–90% content of In by using picosecond transient grating technique. The observed faster recombination rate in alloys with higher Ga content and formation of a thermal grating via a lattice heating, being more pronounced for layers with larger band gap, indicated that the main reason of the heating is not the excess energy of photons, but the defect density which increases with Ga content. A gradual decrease in carrier lifetime with excitation or with increasing temperature in 50–300 K range point out the role of potential barriers in carrier recombination.

The new route process of V3Ga mono-cored and multifilamentary wires using high Ga content Cu-Ga compound and V matrix precursor

V3Ga compound is one of the attractive low activation materials for high magnetic field superconducting magnet in the several V-based compounds because V-based superconducting materials have shorter decay time of induced radioactivity and high field property above 20 T. V3Ga compound has not only high upper critical magnetic fields (Hc2) above 20 T as well as Nb3Sn but also better mechanical property. However, the present critical current density (Jc) property of V3Ga compound wire is insufficiency to apply for large high field magnet such as fusion application. In the previous study, V3Ga compound wire was mainly investigated ‘Diffusion process’ between Cu-Ga solid solution matrix within 20 at% Ga composition and V filament. Recently, we investigated the new route PIT process using high Ga content Cu-Ga compound to fabricate V3Ga mono-cored and multifilamentary wires in order to increase a volume fraction of synthesized A15 phase. It was confirmed that the thicker V3Ga layer formed along the boundary of Cu-Ga powder core and V matrix compared with previous diffusion processed samples in the case of the both mono-cored and mltifilamentary wires. And Hc2 property of the samples using high Ga content Cu-Ga compounds was increased with increasing of Ga content into Cu-Ga compounds, and it showed about 23.0 T which value was 2.0 T higher than conventional processed samples.

Structural and optical properties of In-rich InGaN nanodots grown by metallo-organicchemical vapor deposition

The surface morphologies, alloy compositions and emission properties of In-richInxGa1−xN nanodots (x≥0.87) grown by metallo-organic chemical vapor deposition at various growth temperatures(550–750 °C) were investigated. We found that the nucleation of InGaN dots was dominated by thesurface migration of In adatoms. A higher Ga content can be achieved at lower growthtemperatures due to the relatively lower migration ability of Ga adatoms. At higher growthtemperatures, the InGaN dots tend to decompose into In-rich islands and a thin Ga-richlayer. These In-rich islands exhibit photoluminescence emission in the near-infrared range.Another visible emission band was also observed for samples grown at higher temperatures.The formation of a thin Ga-rich layer is likely to be responsible for the visible emission.

Effects of Ga content on Cu(In,Ga)Se 2 solar cells studied by numerical modeling

The band-gap energy of the CuIn 1− x Ga x Se 2 (CIGS) films is varied in the range from 1.04 to 1.68 eV with the corresponding Ga content in the CIGS films from x=0 to 1. With the addition of Ga in the CuInSe 2 films for the CIGS-based solar cells, the high open-circuit voltage is achieved, and hence the performance of the CIGS solar cells is improved. However, the performance of the CIGS solar cells with the high Ga content falls short of the expectations. The simulation results suggest that the defect density in the surface layers and/or the bulk defect density of the CIGS films are the critical factors responsible for the limitation of the performance for the CIGS solar cells with the high Ga content. Due to the surface band-gap widening, the conduction band offset between the surface region and bulk region of the CIGS films is formed. The simulation results indicate that the open-circuit voltage of the CIGS solar cells increases with the increase of the conduction band offset. The band-gap grading in the space charge region and near the back surface region with the spatial gradient distribution of the Ga content significantly improves the performance of the CIGS solar cells.

Fabrication and superconducting properties ofPIT-V3Ga mono-cored wires using high Ga content Cu–Ga compound powders

V-based superconducting material has a shorter decay time of induced radioactivity and itsmechanical properties are better than Nb-based materials. We thought that theV3Ga compound was one of the most promising materials in ‘low activation and higher fieldsuperconductors’ for an advanced fusion reactor. However, the present critical current density(Jc) propertyof the V3Ga compound wire is insufficient to apply to fusion magnet applications.We investigated a new route powder-in-tube (PIT) process using a highGa content Cu–Ga compound in order to improve workability and theJc propertyof the V3Ga compound wire. It was confirmed that a thicker reaction layer formed along the boundaryof the Cu–Ga compound powder filament and V matrix. Critical transition temperature(Tc) values were shown to be almost 15 K, which was higher thanconventional bronze processed samples. Comparisons of the transportJc property and microstructure between different Ga content Cu–Ga compounds areinvestigated in this paper.

Tomato fruit set driven by pollination or by the parthenocarpic fruit allele are mediated by transcriptionally regulated gibberellin biosynthesis

We investigated the role of gibberellins (GAs) in the phenotype of parthenocarpic fruit (pat), a recessive mutation conferring parthenocarpy in tomato (Solanum lycopersicum L.). Novel phenotypes that parallel those reported in plants repeatedly treated with gibberellic acid or having a GA-constitutive response indicate that the pat mutant probably expresses high levels of GA. The retained sensitivity to the GA-biosynthesis inhibitor paclobutrazol reveals that this condition is dependent on GA biosynthesis. Expression analysis of genes encoding key enzymes involved in GA biosynthesis shows that in normal tomato ovaries, the GA20ox1 transcript is in low copy number before anthesis and only pollination and fertilization increase its transcription levels and, thus, GA biosynthesis. In the unpollinated ovaries of the pat mutant, this mechanism is de-regulated and GA20ox1 is constitutively expressed, indicating that a high GA concentration could play a part in the parthenocarpic phenotype. The levels of endogenous GAs measured in the floral organs of the pat mutant support such a hypothesis. Collectively, the data indicate that transcriptional regulation of GA20ox1 mediates pollination-induced fruit set in tomato and that parthenocarpy in pat results from the mis-regulation of this mechanism. As genes involved in the control of GA synthesis (LeT6, LeT12 and LeCUC2) and response (SPY) are also altered in the pat ovary, it is suggested that the pat mutation affects a regulatory gene located upstream of the control of fruit set exerted by GAs.

Accumulation of trace elements used in semiconductor industry in Formosan squirrel, as a bio-indicator of their exposure, living in Taiwan

Concentrations of 17 trace elements were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) in Formosan squirrels (Callosciurus erythraeus) of Taiwan and Japan to document trace element pollution in Taiwan. High concentrations of elements used to produce semiconductors - Ga, As, Cd, In and Tl - were found in animals captured in Miaoli County, which is the nearest site to Hsinchu City, a chief city of Taiwan's semiconductor industry. Significant correlations between Ga, As, In and Tl were found in the kidney, liver, lung and muscle tissues of Taiwanese squirrels. Hierarchical cluster analysis indicated that Ga, As, In and Tl were of the same clade, indicating that Ga, As, In and Tl were discharged from an identical origin. Molar ratios of Ga/As concentration in lungs of animals captured in Miaoli resembled those of animals after intratracheal administration of particulate gallium arsenide (GaAs). This result might indicate that the higher concentrations of Ga and As in the specimens in Miaoli resulted from atmospheric exposure to GaAs.

Geochemistry and mineralogy of the Late Permian coals from the Songzo Coalfield, Chongqing, southwestern China

Mineralogy and geochemistry of the four main workable coal seams (No.6, No.7, No.8, and No.11) of Late Permian age from the Songzao Coalfield, Chongqing, Southwest China, were examined using inductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), cold-vapor absorption spectrometry (CV-AAS), ion-selective electrode (ISE), scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDX), and X-ray diffraction analysis (XRD). The results showed that the main workable No.8 Coal that accounts for about 60% of the total coal reserves in the Songzao Coalfield was not enriched in hazardous trace elements. The No.11 Coal has high concentrations of alkaline elements, Be (9.14 μg/g), Sc (12.9 μg/g), Ti (9508 μg/g), Mn (397 μg/g), Co (23.7 μg/g), Cu (108 μg/g), Zn (123 μg/g), Ga (32 μg/g), Zr (1304 μg/g), Nb (169 μg/g), Hf (32.7 μg/g), Ta (11.4 μg/g), W (24.8 μg/g), Hg (0.28 μg/g), Pb (28.1 μg/g), Th (24.1 μg/g), and rare earth elements (509.62 μg/g). The concentration of Nb and Ta in the No. 11 Coal is higher than the industrial grade, and their potential utilization should be further studied. Besides pyrite, quartz, calcite, and clay minerals, trace minerals including chalcopyrite, marcasite, siderite, albite, mixed-layer clay minerals of illite and smectite, monazite, apatite, anatase, chlorite, and gypsum were found in the No.11 Coal. It should be noted that alabandite of hydrothermal origin and anatase occurring as cement were identified in coal. In addition, the clayey microbands derived from alkaline volcanic ashes were identified in the coal. The dominant compositions of these clayey microbands were mixed-layer clay minerals of illite and smectite, which were interlayered with organic bands. The modes of occurrence of alkaline volcanic ash bands indicate that the volcanic activities were characterized by the multiple eruptions, short time interval and small scale for each eruption during peat accumulation. The alkaline volcanic ashes were the dominant factors for the enrichment of alkaline elements, Nb, Ta, Zr, Hf, and rare earth elements, and the sulfide minerals are the main carriers of Ga, Cu, and Hg in the No. 11 Coal.

Photoluminescence spectra and lifetimes of $${{}^4\hbox{I}_{{13}/2} \rightarrow {}^4\hbox{I}_{{15}/2} }$$ and $${{}^4\hbox{I}_{{11}/2} \rightarrow {}^4\hbox{I}_{{15}/2} }$$ transitions in erbium doped GeGaSe and GeGaS glasses

The steady-state and transient photoluminescence has been investigated in Ge-Ga-Se and Ge-Ga-S chalcogenide glasses with stoichiometric composition and heavily doped with Er. These glasses show the expected characteristics of \({\hbox{Er}^{3+}}\) ion absorption/emission bands. The Judd-Ofelt analysis yields radiative lifetimes of the \({{}^{4}\hbox{I}_{13/2}\rightarrow ^{4}\hbox{I}_{15/2 }}\) transition, \({\tau_{JO} }\). We find \({\tau_{JO} \approx1.8}\) ms for GeGaSe:Er, and \({\tau_{JO} \approx 2.6}\) ms for GeGaS:Er. However, we find that the PL decay after the interruption of excitation shows a characteristic decay time \({\tau_D }\) which is substantially longer than the theoretically predicted \({\tau_{JO} }\) . In the present paper we discuss an energy transfer model which is based on the assumption that the excitation can travel along the system of isolated \({\hbox{Er}^{3+}}\) ions with negligible self-quenching due to successive absorption–emission events caused by optical transitions between \({{}^{4}\hbox{I}_{15/2}}\) and \({{}^{4}\hbox{I}_{13/2 }}\) levels (and vice versa) in \({\hbox{Er}^{3+}}\) ions. We show that the model can effectively explain the experimental data and we make the conclusion that \({\hbox{Er}^{3+}}\) ions in GeGaSe glasses with stoichiometric compositions and high concentration of Ga reside in isolated states and have a negligible rate of non-radiative relaxation from \({{}^{4}\hbox{I}_{13/2 }}\) to \({{}^{4}\hbox{I}_{15/2}}\) and levels.

Iron-uptake in the Euryarchaeon Halobacterium salinarum

Iron-uptake is well studied in a plethora of pro- and eukaryotic organisms with the exception of Archaea, which thrive mainly in extreme environments. In this study, the mechanism of iron transport in the extremely halophilic Euryarchaeon Halobacterium salinarum strain JW 5 was analyzed. Under low-iron growth conditions no siderophores were detectable in culture supernatants. However, various xenosiderophores support growth of H. salinarum. In [55Fe]-[14C] double-label experiments, H. salinarum displays uptake of iron but not of the chelator citrate. Uptake of iron was inhibited by cyanide and at higher concentrations by Ga. Furthermore, a K(M) for iron uptake in cells of 2.36 microM and a Vmax of approximately 67 pmol Fe/min/mg protein was determined. [55Fe]-uptake kinetics were measured in the absence and presence of Ga. Uptake of iron was inhibited merely at very high Ga concentrations. The results indicate an energy dependent iron uptake process in H. salinarum and suggest reduction of the metal at the membrane level.

V3Ga 超伝導線材における高 Ga 濃度 Cu-Ga 化合物粉末を経由した新製法

A superconducting magnet system is also one of the important components in an advanced magnetic confinement fusion reactor. Then it is required to have a higher magnetic field property to confine and maintain the steady-state burning deuterium (D)-tritium (T) fusion plasma in the large interspace during the long term operation. Burning plasma is sure to generate 14 MeV fusion neutrons during deuterium-tritium reaction, and fusion neutrons will be streamed and penetrated to superconducting magnet through large ports with damping neutron energy. Therefore, it is necessary to consider carefully not only superconducting property but also neutron irradiation property in superconducting materials for use in a future fusion reactor, and a “low activation and high field superconducting magnet” will be required to realize the fusion power plant beyond International Thermonuclear Experimental Reactor (ITER). V-based superconducting material has a much shorter decay time of induced radioactivity compared with the Nb-based materials. We thought that the V3Ga compound was one of the most promising materials for the “low activation and higher field superconductors” for an advanced fusion reactor. However, the present critical current density (Jc) property of V3Ga compound wire is insufficient for apply to fusion magnet applications. We investigated a new route PIT process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V3Ga compound wire.

Characteristics of stacked CuInS 2 and CuGaS 2 layers as determined by the growth sequence

CuInS 2 and CuGaS 2 thin films have been prepared sequentially from elemental evaporation sources onto conventional soda lime glass substrates heated at 350 °C during the deposition process. The gradient in the structure and composition of the stacked layers has been investigated for the two possible growth sequences. Structural depth profiling and crystallographic phase analysis were performed by grazing incidence X-ray diffraction. The atomic distribution in the films depth was analyzed by X-ray photoelectron spectroscopy combined with sputter etching. Formation of the quaternary compound CuIn 1 − x Ga x S 2, with a high Ga content x > 0.80, has been detected with different distribution depending on the growth sequence.

Light- and bias-induced metastabilities in Cu(In,Ga)Se2 based solar cells caused by the (VSe-VCu) vacancy complex

We investigate theoretically light- and bias-induced metastabilities in Cu(In,Ga)Se2 (CIGS) based solar cells, suggesting the Se–Cu divacancy complex (VSe-VCu) as the source of this hitherto puzzling phenomena. Due to its amphoteric nature, the (VSe-VCu) complex is able to convert by persistent carrier capture or emission from a shallow donor into a shallow acceptor configuration, and vice versa, thereby changing in a metastable fashion the local net acceptor density inside the CIGS absorber of the solar cell, e.g., a CdS/CIGS heterojunction. In order to establish a comprehensive picture of metastability caused by the (VSe-VCu) complex, we determine defect formation energies from first-principles calculations, employ numerical simulations of equilibrium defect thermodynamics, and develop a model for the transition dynamics after creation of a metastable nonequilibrium state. We find that the (VSe-VCu) complex can account for the light-induced metastabilities, i.e., the “red” and “blue” illumination effects, as well as for the reverse-bias effect. Thus, our (VSe-VCu) model implies that the different metastabilities observed in CIGS share a common origin. A defect state in the band gap caused by (VSe-VCu) in the acceptor configuration creates a potentially detrimental recombination center and may contribute to the saturation of the open circuit voltage in larger-gap Cu(In,Ga)Se2 alloys with higher Ga content. Therefore, the presence of metastable defects should be regarded as a concern for solar cell performance.

Improved germination of Gymnacranthera canarica Warb. an endangered, endemic tree species of Myristica swamps, Western Ghats, India

Gymnacranthera canarica Warb, an endangered, endemic tree species of Western Ghats, India. The species is exclusively associated with swampy conditions and habitat destruction seems to be the major threat. Although seed viability was 98 per cent confirmed by TZ test, initial germination was only 40% suggesting dormancy problem in this species. Among the 14 treatments, seed coat removal itself enhanced germination by 20 per cent (60%) over control (40%) showing partial permeability of seed coat to water. GA(3) @ 50, 100 and 250 ppm with partial removal of seed coat showed significantly higher germination by 39, 33 and 30 per cent respectively over control. However, higher concentration of GA(3) @ 500 ppm showed inhibitory effect (10%). With respect to IAA we fail to observe any pattern in this species. Further, nil germination in boiling water, cold, boiling water+ hormonal treatment confirming the dormancy of seeds. Our results provide means to enhance the seed germination and helps for restoration and conservation of an endangered species in Western Ghats.

Discovery of the superlarge gallium ore deposit in Jungar, Inner Mongolia, North China

Mineralogy and geochemistry of No.6 Coal from the Heidaigou Mine of the Jungar Coalfield of North China were studied using instrumental neutron activation analysis, inductively coupled-plasma mass spectroscopy, X-ray fluorescence spectrometry, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The results show that gallium concentration is as high as 44.8 μg·g−1 in the whole coal-channel sample, and varies from 30.1 μg·g−1 to 76.0 μg·g−1 (mean 51.9 μg·g−1) in the main minable benches of No.6 Coal. Such high concentration of Ga in the coal is far higher than the industrial grade (30 μg·g−1). The thickness of the main minable benches accounts for 81.9% of the whole coal bed. The laboratory high-temperature ashes (550°C) of the main minable coal benches also contain a high concentration of Ga, varying from 62.2 μg·g−1 to 178 μg·g−1, with an average of 89.2 μg·g−1. The boehmite significantly enriched in No.6 Coal is the main carrier of the high Ga in the coal. Average concentration of Ga in boehmite is 0.09%. The average content of boehmite is 6.1% in the whole coal and 7.5% in the main minable benches. Boehmite is derived from the bauxite in the weathered crust of the underlying Benxi Formation in the north of the basin during the peat accumulation. The colloidal idrargillite had been shortly transported from the weathered crust to the peat mire, and owing to the compaction of the overlying strata during the peat accumulation and early diagenesis, the idrargillite colloid had begun to be dehydrated, leading to boehmite formation. A preliminary estimation showed that the ensured and prospected reserves of Ga in No.6 Coal are up to 6.3 × 104t and 8.57 × 15t, indicating a superlarge gallium ore deposit. The particular paleogeography of the Jungar Coalfield and the peculiar carrier of Ga in coal suggest that this Ga ore deposit is unique in the world. Rare earth elements are also enriched in coal and laboratory ashes. The weighted average concentration of the total rare earth elements is 255 μg·g−1 and 830.36 μg·g−1 in the main minable benches and their laboratory ashes, respectively. Because Al is the main composition of boehmite, aluminum and rare earth elements in No.6 Coal are also the available and valuable resources.

Metalliferous sediments of the Triassic cherty formation in the Ol’ga ore district of primorye: Tin-noble metal ores of a new genetic type

The Triassic cherty formation of Sikhote Alin [1] hosts metalliferous deposits. They are commonly represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues (primarily, consisting of Mn-silicates and aluminosilicates) with high concentrations of Ga, Au, Pt, Pd, and other metals [3]. In the Ol’ga district, the metalliferous deposits are also represented by chocolate-brown siliceous rocks (hereafter, brown cherts) and tin‐iron ores. The metalliferous deposits occur in the Middle‐ Late Triassic siliceous‐clayey sequence. They make up at least one ore-bearing unit (thickness of 5 m or more) represented by brown cherts with a manganese rock bed near the upper contact. The overlying tin‐iron ore bed varies from tens of centimeters to a few meters in thickness. Judging from locations of native exposures, talus, and alluvial fragments, the ore-bearing unit is developed over an area of no less than 20 km 2 (Fig. 1). The manganese rocks are composed of rhodonite, pyroxmangite, and spessartine with a maximum V 2 O 3 content of 0.20 wt % [2, 4]. The rocks contain kanoite, tephroite, manganactinolite, dannemorite, tirodite, pyrosmalite, pyrophanite, hubnerite, scheelite, native silver, native gold, minerals of the cobaltite‐ gersdorffite series, pentlandite, millerite, violarite, tetradymite, tellurobismuthite, and other minerals. The manganese rocks also include Au (up to 35 g/t), Pt (0.08‐ 0.33 g/t), Zn (up to 5.97 wt %), Cu (up to 0.64 wt %), Ni (up to 0.14 wt %), and Co (up to 0.10 wt %) [3]. Nearly all polished samples contain native silver dissemination up to 20 µ m in diameter. Gold grains ( n mm in size) extracted by the acid treatment of manganese rocks are characterized by a high grade of fineness

Microstructure evolution in CoNiGa shape memory alloys

Magnetic shape memory CoNiGa alloys hold great promise as new smart materials due to the good ductility and a wide range of martensitic transformation (MT) temperatures as well as magnetic transition points. This paper reports the results of investigations on the equilibrium phase constitution and microstructure evolution in quenched or aged CoNiGa alloys using the optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods. The dendritic γ phase decreases as lowering of Ga content in studied two series of samples (Co 50Ni 50 − x Ga x , x = 0–50 and Co 100 − 2 y Ni y Ga y , y = 15–35). Some γ′ precipitates with different morphologies were found in given alloys conducted with water quenching (WQ) at 800 °C or long-time ageing at 300 °C. After 800 °C quenching, the γ′ phase has a rod-like shape for the Co 50Ni 30Ga 20 alloy but shows a Widmanstätten morphology as Ga increases to 25 at%, and trends to be block structure in further high Ga content alloy. In the case of 300 °C aged alloys, the γ′ particles prefer to nucleate in interior of γ phase or at the interface of β–γ. We also presented an illustrative vertical section phase diagram keeping 50 at% Co, and isothermal section phase diagram at 1150 and 800 °C of the CoNiGa system. Based on the schematic ternary phase diagram, the composition scope which potentially holds over the magnetic pure martensite phase structure at room temperature (RT) was pointed out. It is believed that this optimized range alloys would play an important role in the functional materials design for application.