- Low temperature growth of single crystalline germanium nanowires
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Ge nanowires have been prepared at a low temperature by a simple hydrothermal deposition process using Ge and GeO2 powders as the starting materials. These as-prepared Ge nanowires are single crystalline with the diameter ranging from 150 nm to 600 nm and length of several dozens of micrometers. The photoluminescence spectrum under excitation at 330 nm shows a strong blue light emission at 441 nm. The results of the pressure and GeO2 content dependences on the formation and growth of Ge nanowires show that the hydrothermal pressure and GeO2 content play an essential role on the formation and growth of Ge nanowires under hydrothermal deposition conditions. The growth of Ge nanowires is proposed as a solid state growth mechanism.
- Pei,Zhao,Tan,Yu,Chen,Wang,Fan,Chen,Zhang, Qian-Feng
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- High quality Ge on Si by epitaxial necking
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We show that pure Ge grown selectively on SiO2/Si substrates in 100 nm holes is highly perfect at the top surface compared to conventional Ge lattice-mismatched growth on planar Si substrates. This result is achieved through a combination of interferometric lithography SiO2/Si substrate patterning and ultrahigh vacuum chemical vapor deposition Ge selective epitaxial growth. This epitaxial necking, in which threading dislocations are blocked at oxide sidewalls, shows promise for dislocation filtering and the fabrication of low-defect density Ge on Si. Defects at the Ge film surface only arise at the merging of epitaxial lateral overgrowth fronts from neighboring holes. These results confirm that epitaxial necking can be used to reduce threading dislocation density in lattice-mismatched systems.
- Langdo,Leitz,Currie,Fitzgerald,Lochtefeld,Antoniadis
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- Synthesis of crystalline and amorphous germanium nanorods
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Crystalline and amorphous germanium nanorods have been synthesized by PVD of germanium powders in flowing Ar/H2 atmospheres. TEM images show diameters of the nanorods ranging from 20 to 200 nm and length up to 5 μm. Selected area electron diffraction indicates that the crystalline nanorods have tetragonal structure. Their growth process has been considered as VLS mechanism. Published by Elsevier Science Ltd.
- Wu, Xingcai,Tao, Yourong
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- SiF4-Sensitized Decomposition of GeH4 by a Pulsed CO2 TEA Laser1,2
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The decomposition of GeH4, sensitized by multiphoton absorption of unfocused infrared laser radiation by SiF4, has been studied in the fluence range 0.2-0.9 J/cm2 and over a total pressure range of 1-70 Torr.Strong absorption of energy from a pulser CO2 laser photon field (P40 line; 1027.4 cm-1) and subsequent energy-transfer processes cause an increase in the temperature of the system.As a result of these processes, decomposition of GeH4 occurs leading to the formation of stoichiometric amounts of metallic germanium and molecular hydrogen.The effects of initial composition, pressure, fluence, and presence of foreign gases (He, H2) on the yield of GeH4 decomposition were examined.A reaction model is proposed which assumes that molecules initially present in the absorption volume are heated by the laser pulse and subsequently decompose unimolecularly.Since the decomposition process is exothermic, it prompts a futher increase in temperature and thus enhances the decomposition process.Both absorption and decomposition create a shock wave causing expansion of hot gas into cool surrounding volume.The latter process brings about cooling of the hot gas and quenches the decomposition process.Taking into account the above-mentioned effects the temperature profiles (T versus time and geometry of the reaction zone) were evaluated on the basis of statistical thermodynamics, assuming that, at any stage, the system attains thermal equilibrium.Yields of decomposition were then derived with kuni values calculated by the RRKM method.The proposed approach accounts satisfactorily for the experimentally observed dependencies, and we believe it can be generally applied to the description of photosensitized process in the infrared region.
- Blazejowski, J.,Lampe, F. W.
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- Benchtop electrochemical liquid-liquid-solid growth of nanostructured crystalline germanium
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An electrochemical liquid-liquid-solid (ec-LLS) process that produces large amounts of crystalline semiconductors with tunable nanostructured shapes without any physical or chemical templating agent is presented. Electrodeposition of Ge from GeO2(aq) solutions followed by dissolution into a liquid Hg electrode, saturation of the liquid alloy, and precipitation can yield polycrystalline Ge(s) under ambient conditions. A unique advantage of ec-LLS is that it involves precipitation under electrochemical control, where the applied bias precisely defines the flux of Ge into the liquid electrode. Fidelity of the saturation and precipitation of Ge from liquid electrodes affords a variety of material morphologies, including dense films of oriented nanostructured filaments with large aspect ratios (>103). Electrodeposition involving a liquid electrolyte, a liquid electrode, and a solid deposit under ambient conditions represents a conceptually unexplored direct wet-chemical route for the preparation of bulk quantities of crystalline group-IV semiconductors without the time- and energy-intensive processing steps required in traditional preparations of semiconductor materials.
- Carim, Azhar I.,Collins, Sean M.,Foley, Justin M.,Maldonado, Stephen
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- On direct-writing methods for electrically contacting GaAs and Ge nanowire devices
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The electronic transport and gating characteristics in GaAs and Ge nanowires (NWs) are altered significantly following either indirect or direct exposure to a focused Ga+ ion beam (FIB), such as that used to produce Pt electrical contacts to NWs. While these results challenge the assumptions made in some previously reported work relating to the electronic properties of semiconductor NWs using FIB-assisted production of contacts and/or their leads, local electron beam induced deposition is shown to be a reliable and facile route for producing robust electrical contacts to individual vapor phase-grown NWs in a manner that enables study of their actual carrier transport properties.
- Chen, Guannan,Gallo, Eric M.,Burger, Joan,Nabet, Bahram,Cola, Adriano,Prete, Paola,Lovergine, Nico,Spanier, Jonathan E.
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- Formation of nickel germanide contacts to Ge nanowires
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Nickel germanide contacts are expected to play an important role in Ge-based electronics similar to that of their nickel silicide counterparts in Si devices. Here we have studied the solid state reaction between Ni contact pads and Ge nanowires. We observ
- Dellas,Minassian,Redwing,Mohney
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- Influence of defects and interface on radiative transition of Ge
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The influences of defects and surface roughness on the indirect bandgap radiative transition of Ge were studied. Bulk Ge has 15 times the integrated intensity of photoluminescence of Ge-on-Si. However, for Ge-on-Si sample, the direct transition related ph
- Jan,Chen,Lee,Chan,Peng,Liu,Yamamoto,Tillack
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- Application of n-dodecyltrimethylammonium chloride for the oxidation of intermetallic phases
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The thermal decomposition products of ionic liquids based on n-dodecyltrimethylammonium chloride (DTAC) were used for the preparation of the metastable allotrope Ge(cF136) by oxidation of Na12Ge17 in gas-solid reactions. This method of preparation provides a promising low-temperature route for the synthesis of intermetallic phases and elemental modifications. In order to explore the reaction mechanism, we investigated the thermal decomposition of DTAC as well as of the ionic liquids DTAC/MgCl 2 and DTAC/AlCl3 by in-situ mass spectrometry and by powder X-ray diffraction. The results have revealed HCl, CH3Cl and 1-chlorododecane to act as oxidizing agents in the gas-solid redox reactions.
- Boehme, Bodo,Hoffmann, Stefan,Baitinger, Michael,Grin, Yuri
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- Influence of HCl on the chemical vapor deposition and etching of Ge islands on Si(001)
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When HCl is added during the growth of Ge islands on Si(001) by chemical vapor deposition, the reduced Ge surface diffusion impedes island development. There is a shift in the relative populations of different island types even when other conditions such as temperature, coverage, and growth rate, are unchanged. The effect of HCl on the net rate of deposition is proportional to the square of the HCl partial pressure, suggesting a surface reaction with the Ge. When larger islands are etched with HCl at high enough temperature, they revert to a shape characteristic of smaller islands, confirming the reversibility of transformations from one island type to another. It has not proved possible to use etching to produce smaller and more uniform islands.
- Kamins,Briggs,Williams, R. Stanley
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- HIGH-PRESSURE SYNTHESIS AND CRYSTAL STRUCTURE OF VGe2 AND Cr4Ge7.
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The new germanides, Cr//4Ge//7 with the defect disilicide-type structure and VGe//2 with the C40 structure, are synthesized at 4-5. 5 GPa and 800-1100 degree C for 1-3 hr using the belt-type high-pressure apparatus. The relationship between the chemical c
- Takizawa,Sato,Endo,Shimada
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- Low-temperature synthesis of Ge nanocrystals in zeolite Y
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A method for obtaining Ge nanocrystals has been developed using the porous structure of zeolite Y as a matrix. Samples were obtained by reduction of GeO2 nanocrystals, previously grown in zeolite α cages, in H2 at 470°C. This is apparently the lowest GeO2 reduction temperature reported and is probably due to the influence of the host. Ge crystallites so formed present an absorption edge at 2.2 eV, which is shifted ~1.4 eV with respect to the bulk value. A softening and an asymmetric broadening of the Raman peak were also observed. We can estimate an average diameter of 3 nm for the Ge nanocrystals from both results.
- Miguez,Fornes,Meseguer,Marquez,Lopez
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- Influence of surface states on electron transport through intrinsic Ge nanowires
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Solution-grown single-crystal Ge nanowires were used as conductive channels in field effect transistor devices to study the influence of surface states on their electron transport properties. Nanowires contacted with Pt electrodes using focused ion beam metal deposition exhibited linear current-voltage (IV) curves at room temperature with apparent resistivities ranging from 101 to 10-1 ? cm. In all cases, the nanowire conductance decreased with positive external electric fields applied perpendicular to the nanowire surface by a gate electrode, characteristic of p-type carrier accumulation at the nanowire surface. The field-induced change in conductance exhibited a time-dependent relaxation, with response time and magnitude of current decrease that depended on the nanowire surface chemistry. Nanowires treated with an organic passivation layer using a thermally initiated hydrogermylation reaction exhibited 2 orders of magnitude slower current relaxation and a smaller decrease in current relative to bare nanowires with oxidized surfaces. ? 2005 American Chemical Society.
- Hanrath, Tobias,Korgel, Brian A.
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- Fabrication of uniform Ge-nanocrystals embedded in amorphous SiO 2 films using Ge-ion implantation and neutron irradiation methods
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Uniform Ge-nanocrystals (Ge-ncs) embedded in amorphous SiO2 film were formed by using G 74e+ ion implantation and neutron transmutation doping (NTD) method. Both experimental and theoretical results indicate that the existence of As dopants transmuted from G 74 e by NTD tunes the already stabilized (crystallized) system back to a metastable state and then activates the mass transfer processes during the transition form this metastable state back to the stable (crystallized) state, and hence the nanocrystal size uniformity and higher volume density of Ge-ncs. This method has the potential to open a route in the three-dimensional nanofabrication.
- Chen,Lu,Xu,Meng,Hu,Sun,Shlimak
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- Ba8Ge43 revisited: A 2a′x2a′x2a′ superstructure of the clathrate-I type with full vacancy ordering
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The reinvestigation of the crystal structure of Ba8Ge 43□3 (space group Ia3d, no. 230; a = 21.3123(5) A; Z = 8; Pearson symbol cI408) shows a full ordering of the vacancies (□) in the germanium framework. This ordered crystal structure can be considered as a derivative of an ideal Ba8Ge46 clathrate-I type structure (Pm3n, a′ = a/2) in which three Ge vacancies (per formula unit) are allowed to order in a cubic superstructure with a doubled unit cell parameter (□ at the 24c site, space group Ia3d). In the resulting Ge framework, each vacancy □ is surrounded by four three-bonded (3b)Ge - species. The ordering in crystals of as-cast samples (cooled in argon atmosphere, non-annealed) is partially disrupted. For the as-cast crystals, a short-range model is proposed based on the partial distribution of Ge on the 24c and 24d sites. From the electron balance, Ba8Ge43 can be considered as a metallic Zintl phase with four excess electrons per formula unit. The Ba8Ge43 phase is stable in the temperature range 770-810°C and exists in equilibrium with Ba6Ge25 and Ge. By decomposition of undercooled (metastable) Ba8Ge43, a new metastable binary BaGe ~5 phase is formed.
- Carrillo-Cabrera, Wilder,Budnyk, Serhij,Prots, Yurii,Grin, Yuri
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- Atomic force microscopy and photoluminescence study of Ge layers and self-organized Ge quantum dots on Si(100)
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In this letter we present an atomic force microscopy and photoluminescence investigation of two- and three-dimensional Ge structures deposited on Si(100) substrates. The photoluminescence spectra demonstrated the presence of quantum confinement effects in flat and uncapped Ge layers and in Ge islands even for the relatively large size of the structures. Moreover, a correlation between the sample morphology and the features of the photoluminescence is demonstrated.
- Palange,Capellini,Di Gaspare,Evangelisti
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- Peculiarities of thermal decomposition of inorganic and organometallic compounds of GeIV and GeII. Thermolysis of (acac) 2GeX2 (X = Cl, N3) and (CO) 5MGeCl2(thf) (M = Cr, Mo, W)
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Thermal decomposition of the complexes (acac)2Ge(N 3)2 (1), (acac)2GeCl2 (2), and (CO)5M=GeCl2(THF) (M = Cr (3), Mo (4), W (5)) was studied by differential scanning calorimetry a
- Dobrokhotova,Koroteev,Saushev,Aleksandrov,Novotortsev,Nefedov,Egorov
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- Electrodeposition of stable and narrowly dispersed germanium nanoclusters from an ionic liquid
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Germanium nanoclusters with a narrow height distribution have been electrodeposited from a dilute solution of GeCl4 in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIm]PF6: under the reported conditions the lateral sizes of most of the clusters range between 20 and 30 nm while their heights vary from 1 to 10 nm with most of them between 1 and 5 nm.
- Endres, Frank,Zein El Abedin, Sherif
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- Synthesis, structural characterization, and thermal properties of the first germanium N,N,N′,N′-tetraalkylguanidinates
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The first examples of germanium N,N,N′,N′- tetraalkylguanidinates have been prepared, and two of them have been structurally characterized. All of them exihibit high stability and volatility. Their potential as low-temperature precursors for MOCVD of Ge a
- Chen, Tianniu,Hunks, William,Chen, Philip S.,Xu, Chongying,DiPasquale, Antonio G.,Rheingold, Arnold L.
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- On the oxidation of Ti2GeC in air
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Herein we report on the oxidation of bulk Ti2GeC in air in the 600 ° C to 800 °C temperature range. At 600 °C, and up to 500 h, the oxidation kinetics are sub-parabolic and the rutile TiO2 layer formed is adherent and protective. At 700 °C and 800 °C the kinetics are parabolic up to 100 h before becoming linear. Xray diffraction confirmed the presence of two rutile structures, TiO2 and GeO2, and a hexagonal GeO2 on the oxidized surfaces. The oxidation occurs by inward diffusion of oxygen through a rutile (Ti1-xGex)O2 solid solution with x 6 0.07. Additionally, and throughout the entire temperature range studied, an oxygen- induced decomposition - occurring predominantly at the oxide/carbide interface - results in the formation of an elemental Ge-rich phase. If the rutile layer is not protective, the latter oxidizes into hexagonal GeO2.
- Anasori, Babak,Caspi, El'ad N.,Elraheb, Yasmine,Barsoum, Michel W.
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- Growth of germanium nanowires using liquid GeCl4 as a precursor: The critical role of Si impurities
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Liquid GeCl4 precursors have been employed to grow into one dimensional Ge nanowires (NWs) via a vapor-liquid-solid (VLS) process, in which Si, supplied as a form of liquid SiCl4, plays a critical role for the successful formation of Ge NWs. The Royal Society of Chemistry 2009.
- Song, Hyun Jae,Yoon, Seok Min,Shin, Hyun-Joon,Lim, Hyunseob,Park, Chibeom,Choi, Hee Cheul
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- Macroporous germanium by electrochemical deposition
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Germanium is electrodeposited in a template formed from a dried suspension of silica spheres. The germanium completely fills the pores of the silica matrix. The semiconductor, as deposited, is amorphous but can be crystallized by annealing. Selective dissolution of the silica template gives a macroporous germanium-air sphere matrix, which offers interesting possibilities for photonic applications.
- Van Vugt,Van Driel,Tjerkstra,Bechger,Vos,Vanmaekelbergh,Kelly
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- Fast and safe synthesis of micron germanium in an ammonia atmosphere using Mo2N as catalyst
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Here, we reported a new method for fast and safe synthesis of a micron germanium (Ge) semiconductor. The Ge was successfully prepared from mixed GeO2 with a low amount of MoO3 by the NH3 reduction method at 800 °C for an ultra-short time of 10 min. XRD patterns show that the Ge has a tetragonal structure. SEM images show that the size of the Ge particles is from 5 μm to 10 μm, and so it is on the micron scale. UV-visible diffuse reflectance spectroscopy shows that the Ge has good light absorption both in the ultraviolet and visible regions. The formation of Ge mainly goes through a two-step conversion in the NH3 flow. Firstly, GeO2 is converted to Ge3N4, and then Ge3N4 is decomposed to generate Ge. The comparison experiments of MoO3 and Mo2N demonstrate that Mo2N is the catalyst for the Ge synthesis which improves the Ge3N4 decomposition. The presented fast and safe synthesis method of Ge has great potential for industrialization and the proposed Mo2N boosting the Ge3N4 decomposition has provided significant guidance for other nitride decomposition systems.
- Ma, Baojun,Li, Dekang,Wang, Xiaoyan,Lin, Keying
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- Unseeded growth of germanium nanowires by vapor-liquid-solid mechanism
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Single-crystal germanium nanowires have been synthesized in the temperature range 380-430°C without the use of any metal catalysts. Tetraethylgermane was used as a precursor in combination with different organic solvents to produce nanowires with controlled diameter ranging from 5 nm to 700 nm. The growth direction of nanowires is along 〈011〉 direction. The method is based on the vapor-liquid-solid mechanism, with the classical liquid-metal catalyst replaced by droplets of high-boiling-point hydrocarbons.
- Zaitseva,Harper,Gerion,Saw
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- Kinetic frustration of Ostwald ripening in Ge/Si(100) hut ensembles
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We show that low area density Ge/Si(100) island ensembles comprised solely of hut and pyramid clusters do not undergo Ostwald ripening during days-long growth temperature anneals. In contrast, a very low density of large, low chemical potential Ge islands
- McKay, Michael R.,Venables,Drucker, Jeff
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- Synthesis and photoluminescent properties of size-controlled germanium nanocrystals from phenyl trichlorogermane-derived polymers
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We report the preparation of luminescent oxide-embedded germanium nanocrystals (Ge-NC/ GeO2) by the reductive thermal processing of polymers derived from phenyl thchlorogermane (PTG, C6H 5-GeCl3). Sol-gel processing of PTG yields air-stable polymers with a Ge:O ratio of 1:1.5, (C6H5GeO 1.5)n, that thermally decompose to yield a germanium rich oxide (GRO) network. Thermal disproportionation of the GRO results in nucleation and initial growth of oxide-embedded Ge-NC, and subsequent reaction of the GeO2 matrix with the reducing atmosphere results in additional nanocrystal growth. This synthetic method affords quantitative yields of composite powders in large quantities and allows for Ge-NC size control through variations of the peak thermal processing temperature and reaction time. Freestanding germanium nanocrystals (FS-Ge-NC) are readily liberated from Ge-NC/GeO2 composite powders by straightfoward dissolution of the oxide matrix in warm water. Composites and FS-Ge-NC were characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), and photoluminescence (PL) spectroscopy.
- Henderson, Eric J.,Hessel, Colin M.,Veinot, Jonathan G. C.
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- Diamond-hexagonal semiconductor nanocones with controllable apex angle
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We report on the synthesis of nanostructured and crystalline tapered Si and Ge polyhedra via metal-catalyzed chemical vapor deposition. These Si and Ge nanocones (SiNCs, GeNCs) possess tips with near-atomic sharpness, micron-scaled bases, hexagonal cross-
- Cao, Linyou,Laim, Lee,Ni, Chaoying,Nabet, Bahram,Spanier, Jonathan E.
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- HIGH-PRESSURE SYNTHESIS AND ELECTRICAL AND MAGNETIC PROPERTIES OF MnGe AND CoGe WITH THE CUBIC B20 STRUCTURE.
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MnGe and CoGe with the cubic B20 structure were synthesized at 4-5. 5 GPa and 600-1000 degree C for 1-3 hr using the belt-type high-pressure apparatus. Both MnGe and CoGe are antiferromagnetic with Neel temperatures of 197 and 120 K, respectively. One expects an electron transfer of 0. 7 electron from germanium to transition metal in these compounds. The anomalous temperature dependences of the electrical resistivity, the thermoelectric power, and the magnetic susceptibility of MnGe and CoGe are due to a 'temperature-induced local moment. '
- Takizawa, H.,Sato, T.,Endo, T.,Shimada, M.
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- An alternative method to grow Ge thin films on Si by electrochemical deposition for photonic applications
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Germanium films several micrometers in thickness were electrochemically deposited on silicon wafers for the first time without catalysts and at room temperature from a solution containing Ge species that have been electrochemically dissolved from Ge target. The films were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. SEM images show that the deposited products presented different structures (Flower-like, spheres, and thin films) depending on the current density. XRD reveals that the germanium electrodeposits were of polycrystalline structure and have the preferred crystallographic growth orientation of (220). The grown films were deposited with nickel contact electrodes for characterization as Metal semiconductor Metal (MSM) photodiodes. The current-voltage (I-V) measurements showed the ability to efficiently detect both UV and visible photons. The low deposition temperature, the ease of thickness control, and the inherent advantage of spatial selectivity of the electrodeposition process make this method a promising way to selectively grow high-quality germanium for electronic device applications.
- Jawad,Hashim,Ali,Crcoles,Sharifabad, Maneea E.
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- Nonthermal plasma synthesis of size-controlled, monodisperse, freestanding germanium nanocrystals
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Germanium nanocrystals may be of interest for a variety of electronic and optoelectronic applications including photovoltaics, primarily due to the tunability of their band gap from the infrared into the visible range of the spectrum. This letter discusses the synthesis of monodisperse germanium nanocrystals via a nonthermal plasma approach which allows for precise control of the nanocrystal size. Germanium crystals are synthesized from germanium tetrachloride and hydrogen entrained in an argon background gas. The crystal size can be varied between 4 and 50 nm by changing the residence times of crystals in the plasma between ~30 and 440 ms. Adjusting the plasma power enables one to synthesize fully amorphous or fully crystalline particles with otherwise similar properties.
- Gresback, Ryan,Holman, Zachary,Kortshagen, Uwe
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- Concentration-dependent size control of Germanium nanocrystals
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A room temperature solution phase preparation of germanium nanocrystals has been examined by means of varying the germanium precursor concentration. By varying the germanium tetrachloride concentration, it is possible to control the size distribution of nanocrystals formed. Copyright
- Hope-Weeks, Louisa J.
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- Effects of postgate dielectric treatment on germanium-based metal-oxide-semiconductor device by supercritical fluid technology
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Supercritical fluid (SCF) technology is employed at low temperature as a postgate dielectric treatment to improve gate SiO2 /germanium (Ge) interface in a Ge-based metal-oxide-semiconductor (Ge-MOS) device. The SCF can transport the oxidant and penetrate the gate oxide layer for the oxidation of SiO2 /Ge interface at 150 °C. A smooth interfacial GeO 2 layer between gate SiO2 and Ge is thereby formed after SCF treatment, and the frequency dispersion of capacitance-voltage characteristics is also effectively alleviated. Furthermore, the electrical degradation of Ge-MOS after a postgate dielectric annealing at 450 °C can be restored to a extent similar to the initial state.
- Liu, Po-Tsun,Huang, Chen-Shuo,Huang, Yi-Ling,Lin, Jing-Ru,Cheng, Szu-Lin,Nishi, Yoshio,Sze
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- High yield solution-liquid-solid synthesis of germanium nanowires
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High yields of crystalline Ge nanowires were synthesized for the first time in a conventional solvent of trioctylphosphine by disproportionating GeI2 in the presence of Bi nanoparticle growth seeds at 350 °C and atmospheric pressure. Copyright
- Lu, Xianmao,Fanfair, Dayne D.,Johnston, Keith P.,Korgel, Brian A.
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- Electrochemical preparation of germane
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Germane has been prepared through the electrochemical reduction of the germanate anion in alkaline solutions with a current efficiency of 40-45%. Active solution circulation in the cathodic zone and the use of an Sn or Cd cathode are shown to raise the germane yield. The current density and initial solution concentration have a weak effect on the reduction process.
- Turygin,Smirnov,Shalashova,Khudenko,Nikolashin,Fedorov,Tomilov
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- THE DYNAMICS OF THE SiF4-SENSITIZED PROCESSES INITIATED BY A PULSED CO2 LASER
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A model enabling the examination of the dynamics of the SiF4-sensitized processes initiated by a pulsed CO2 laser is outlined, taking into account three effects: energy absorption, energeticity of chemical reactions and expansion of hot gas created upon interaction of molecules with the infrared photon field.This approach was used to elucidate some aspects regarding the decomposition of PH3 and GeH4.
- Blazejowski, J.,Lampe, F. W.
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- GROWTH AND ETCHING OF GERMANIUM FILMS BY CHEMICAL VAPOR DEPOSITION IN A GeCl4-H2 GAS SYSTEM.
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The etching and growth of germanium films are investigated using a GeCl//4-H//2 gas system in the temperature range of 490 degree -565 degree C. At relatively low GeCl//4 partial pressures less than 2 multiplied by 10** minus **3 torr, epitaxial growth of Ge is observed on Ge (100) surfaces, whereas at GeCl//4 partial pressures higher than 2 multiplied by 10** minus **3 torr, etching of the Ge film is found to occur. In the experiments utilizing patterned substrates, where the surface consists of defined areas of Ge and SiO//2, Ge is found to deposit selectively only on the exposed Ge regions. The growth reactions of Ge epitaxial films proceed through the Langmuir-Hinshelwood mechanism: the surface reaction takes place between two hydrogen atoms dissociatively adsorbed and a surface-adsorbed GeCl//2 molecule.
- Ishii,Takahashi
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- Structure and phase transformation behavior of rapidly solidified alloys in the Ge-Al-La system
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The structure of rapidly solidified Ge-Al-La alloys, as investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), is discussed in comparison with that of Al-Ge-TM (TM = transition metals) alloys. Rapidly solidified Ge-Al-La alloy
- Louzguine, Dmitri V.,Inoue, Akihisa
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- RF-sputter deposition of Zn-Ge nitride thin films
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Nitride Zn-Ge thin films were deposited by reaction sputtering. Black conducting (Zn1-xGex)3N2+δ with x≤0.27 was obtained in a compositional range below 29 wt% Ge against the total metal content. Greenish pale yellow ZnGeN2 was observed in a range of 30-60 wt% Ge. This crystallized in a hexagonal lattice of a comparable size to the isoelectronic GaN. Its solid solution range seems to be very narrow and its band gap was estimated to be about 3.1 eV. Ge3N4, like amorphous (Ge1-yZny)3N4-y with y≤0.43 films, shows pale yellow color above the compositional range of 60 wt% Ge.
- Kikkawa,Morisaka
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- Phenylgermane as a suitable precursor for laser flash photolysis measurements of germylene kinetics
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R. Becerra, S.E. Boganov, M.P. Egorov, O.M. Nefedov and R. Walsh [Chem. Phys. Lett. 260 (1996) 433] reported the first direct kinetic measurements of germylene, GeH2, using two precursors, 3,4-dimethylgermacyclopentene and phenylgermane. They report that phenylgermane produces anomalously low reaction rate constants. We have re-examined this issue and measure rate constants using phenylgermane that agree with the values reported by Becerra et al. using the precursor 3,4-dimethylgermacyclopentene. The first direct rate constant measurement for GeH2+phenylgermane is reported. All rate constants are found to be independent of the total pressure (measured to 50 Torr). Photolysis of phenylgermane at 248 and 193 nm yields the same values for the rate constants within the experimental uncertainty, suggesting that relaxation of vibrationally excited germylene is not altering the measured reaction rate constants.
- Alexander, Ula N.,Trout, Neil A.,King, Keith D.,Lawrance, Warren D.
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- Reactivity and Controlled Redox Reactions of Salt-like Intermetallic Compounds in Imidazolium-Based Ionic Liquids
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Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na12Ge17 as a model system containing redox-sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3-trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na12Ge17 observed on long-time contact with such ILs was not caused by dissolution of the salt-like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na+ ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na12Ge17 were initiated, transferring a considerable part of Na+ into solution. At optimized conditions, an X-ray amorphous product NaGe6.25 was obtained, which was thermally convertible to the crystalline type-II clathrate Na24–δGe136 with almost completely Na-filled polyhedral cages, and α-Ge. The presented method thus provides unexpected access to Na24–δGe136 in bulk quantities.
- Feng, Xian-Juan,Lerch, Swantje,Biller, Harry,Micksch, Maik,Schmidt, Marcus,Baitinger, Michael,Strassner, Thomas,Grin, Yuri,B?hme, Bodo
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- The untypical high-pressure Zintl phase SrGe6
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The binary strontium germanide SrGe6 was synthesized at high-pressure high-temperature conditions of approximately 10 GPa and typically 1400 K before quenching to ambient conditions. At ambient pressure, SrGe6 decomposes in a monotropic fashion at T = 680(10) K into SrGe2 and Ge, indicating its metastable character. Single-crystal X-ray diffraction data indicate that the compound SrGe6 adopts a new monoclinic structure type comprising a unique three-dimensional framework of germanium atoms with unusual cages hosting the strontium cations. Quantum chemical analysis of the chemical bonding shows that the framework consists of three- A nd four-bonded germanium atoms yielding the precise electron count Sr[(4bGe0]4[(3b)Ge-]2 in accordance with the 8-N rule and the Zintl concept. Conflicting with that, a pseudo-gap in the electronic density of states appears clearly below the Fermi level, and elaborate bonding analysis reveals additional Sr-Ge interactions in the concave coordination polyhedron of the strontium atoms.
- Schwarz, Ulrich,Castillo, Rodrigo,Hübner, Julia M.,Wosylus, Aron,Prots, Yurii,Bobnar, Matej,Grin, Yuri
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p. 209 - 216
(2020/02/27)
-
- Size-tunable germanium particles prepared by self-sustaining reduction of germanium oxide
-
Here, we report on a size-controlled synthesis of highly crystalline germanium particles, via the self-sustained reaction of GeO2 with Zn, Mg, and NaBH4. The thermodynamic analysis suggests that the GeO2 + 2Zn and GeO2 + NaBH4 systems are characterized by moderate heats of reaction (?121 and ?204 kJ per mole of Ge, respectively), while GeO2 + 2Mg exhibits a much higher reaction enthalpy (?623 kJ). Magnesium reduction has been found not to be suitable for the preparation of germanium crystals due to the high reaction temperature, which exceeds 2000 °C. The partial substitution of Zn by Mg, however, enables increasing the overall reaction temperature in the low caloric GeO2 +Zn system. By using different reducers and their mixtures, the reaction temperature was optimized to be in the 600–1100 °C range. Such temperature modifications allow for control of the germanium particle sizes, ranging from 200 nm to 2 mm. Thermal analysis of the reacting mixtures and electron microscopy examination of the products indicates that dissolution-precipitation is the dominant formation mechanism of the germanium crystals in the GeO2 + Zn system. The higher reaction temperatures in the GeO2 + Zn + Mg and GeO2 + NaBH4 systems cause melting, and subsequent coalescence of the primarily precipitated germanium resulting in much larger particles.
- Manukyan, Khachatur V.,Schools, Ryan S.,Mukasyan, Alexander S.
-
-
- Metal-Drug Interactions: Synthesis and Spectroscopic Characteristics, Surface Morphology, and Pharmacological Activity of Ephedrine–HCl Complexes with Mo(V), Nb(V), Ga(III), and Ge(IV)
-
Four new Mo(V), Nb(V), Ga(III), and Ge(IV) ephedrine complexes, [Mo(Eph)2(Cl)4].Cl, [Nb(Eph)2(Cl)3], [Ga(Eph)2(Cl)3], and [Ge(Eph)2(Cl)2] are synthesized and characterized. Composition and coordination behavior of ephedrine drug towards Mo(V), Nb(V), Ga(III), and Ge(IV) ions are deduced from microanalysis, IR spectra, molar conductance, magnetic and thermal analysis data. These support coordination of the eph ligand in its neutral state. Ephedrine has two powerful chelating sites, OH and NH, that determine its uni- or bidentate mode of action. IR spectra indicate that Mo(V) and Ga(III) coordinate to ephedrine via nitrogen atom of the NH group as a unidentate chelator with six and five coordination geometry, respectively. On the other hand, Eph ligand behaves as a monoanionic bidentate no chelating agent via the NH and deprotonated OH groups in Nb(V) and Ge(IV) complexes. Mo(V) complex demonstrates electrolytic properties, the other complexes are non-electrolytes in DMSO solutions. TG/DTG analysis makes it possible to calculate the number of solvent molecules in and outside the coordination sphere, and estimate stability of the synthesized complexes. The Eph complexes are screened in vitro for antibacterial (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus) and antifungal (Aspergillus flavus and Candida albicans) activities. Anti-cancer action of the Mo(V) and Ga(III) complexes is assessed against the human hepato cellular carcinoma (HepG-2) tumor cell line (IC50 >1000 μg/mL).
- El-Habeeb,Refat
-
p. 2163 - 2169
(2018/12/11)
-
- Kinetics of germanium tetrachloride reduction with hydrogen in the presence of pyrolytic tungsten
-
Pyrolytic tungsten coatings have been produced on the surface of ash microspheres under steady-state conditions using tungsten hexacarbonyl as a precursor. The nanostructured composites thus obtained were characterized by X-ray diffraction and scanning electron microscopy. We have studied the kinetics of the catalytic reduction of germanium tetrachloride with hydrogen in the temperature range 423–973 K in the presence of the composites as catalysts and determined the reaction order and activation energy for the catalytic reduction of germanium tetrachloride with hydrogen.
- Vorotyntsev,Vorotyntsev,Petukhov,Kadomtseva,Kopersak, I. Yu.,Trubyanov,Ob”edkov,Pikulin,Drozhzhin,Aushev
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p. 919 - 924
(2016/08/16)
-
- Probing lithium germanide phase evolution and structural change in a germanium-in-carbon nanotube energy storage system
-
Lithium alloys of group IV elements such as silicon and germanium are attractive candidates for use as anodes in high-energy-density lithium-ion batteries. However, the poor capacity retention arising from volume swing during lithium cycling restricts their widespread application. Herein, we report high reversible capacity and superior rate capability from core-shell structure consisting of germanium nanorods embedded in multiwall carbon nanotubes. To understand how the core-shell structure helps to mitigate volume swings and buffer against mechanical instability, transmission electron microscopy, X-ray diffraction, and in situ 7Li nuclear magnetic resonance were used to probe the structural rearrangements and phase evolution of various Li-Ge alloy phases during (de)alloying reactions with lithium. The results provide insights into amorphous-to-crystalline transition and lithium germanide alloy phase transformation, which are important reactions controlling performance in this system.
- Tang, Wei,Liu, Yanpeng,Peng, Chengxin,Hu, Mary Y.,Deng, Xuchu,Lin, Ming,Hu, Jian Zhi,Loh, Kian Ping
-
supporting information
p. 2600 - 2607
(2015/03/04)
-
- Honeycomb-like Macro-Germanium as High-Capacity Anodes for Lithium-Ion Batteries with Good Cycling and Rate Performance
-
Macro-Ge powder has been synthesized with a novel hydrothermal reduction of commercial GeO2 at 200°C in an autoclave. The obtained macro-Ge product demonstrates a honeycomb-like macroscopic network structure with a high tap density of 2.19 g cm-3. As for the anode material of lithium ion batteries, the macro-Ge electrode exhibits 1350 mAh g-1 at the current rate of 0.2 C and with 64% capacity retention over 3500 total cycles at 1 C. The macro-Ge contains a honeycomb porous structure, which allows for a high volumetric capacity (~3000 mAh cm-3). Moreover, the symmetrical and asymmetric rate behaviors also provide its excellent electrochemical property. For example, the macro-Ge electrode can be rapidly charged to 1130 mAh g-1 in 3 min (20 C) and 890 mAh g-1 in 90 s (40 C) using the constant discharge mode of 1 C. Furthermore, the Ge electrode still maintains over 1020 mAh g-1 at 1 C for 300 cycles at the high temperature (55°C) environment. When coupled with a commercial LiCoO2 cathode, a 3.5 V lithium-ion battery with capacity retention of 91% (~364 Wh kg-1) over 100 cycles is achieved. These outstanding properties may be attributed to the honeycomb structure, for which the porous architectures supply the high efficient ionic transport and buffers the volume change during the lithiation/delithiation processes. Moreover, with bulk frameworks it ensures the high tap density and further improves the energy density. It is supported that the macro-Ge acts as attractive anode materials for further application in rechargeable lithium ion batteries.
- Liang, Jianwen,Li, Xiaona,Hou, Zhiguo,Zhang, Tianwen,Zhu, Yongchun,Yan, Xuedong,Qian, Yitai
-
p. 4156 - 4164
(2015/06/22)
-
- Alkaline-Earth-Metal-Induced Liberation of Rare Allotropes of Elemental Silicon and Germanium from N-Heterocyclic Metallylenes
-
The synthesis and striking reactivity of the unprecedented N-heterocyclic silylene and germylene ("metallylene") alkaline-earth metal (Ae) complexes of the type [(η5-C5Me5)2Ae←:E(NtBuCH)2] (3, 4, and 7-9; Ae = Ca, E = Ge 3; Ae = Sr, E = Ge 4; Ae = Sr, E = Si 7; Ae = Ba, E = Si 8; Ae = Ba, E = Ge 9) are reported. All complexes have been characterized by spectroscopic means, and their bonding situations investigated by density functional theory (DFT) methods. Single-crystal X-ray diffraction analyses of examples revealed relatively long Si-Ae and Ge-Ae distances, respectively, indicative of weak E:→Ae (E = Si, Ge) dative bonds, further supported by the calculated Wiberg bond indices, which are rather low in all cases (~0.5). Unexpectedly, the complexes undergo facile transformation to 1,4-diazabuta-1,3-diene Ae metal complexes of the type [(η5-C5Me5)2Ae(κ2-{NtBu = CHCH = NtBu})] (Ae = Sr 10, Ae = Ba 11) or in the case of calcium to the dinuclear complex [(η5-C5Me5)2Ca←:N(tBu) = CHCH = (tBu)N:→Ca(η5-C5Me5)2] (12) under concomitant liberation of elemental silicon and germanium. The formation of elemental silicon and germanium is proven by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. Notably, the decomposition of the Si(II)→Ba complex 8 produces allo-silicon, a rare allotropic form of elemental silicon. Similarly, the analogous Ge(II)→Ba complex 9, upon decomposition, forms tetragonal germanium, a dense and rare allotrope of elemental germanium. The energetics of this unprecedented alkaline-earth-metal-induced liberation of elemental silicon and germanium was additionally studied by DFT methods, revealing that the transformations are pronouncedly exergonic and considerably larger for the N-heterocyclic germylene complexes than those of the corresponding silicon analogues. (Figure Presented).
- Blom, Burgert,Said, Amro,Szilvási, Tibor,Menezes, Prashanth W.,Tan, Gengwen,Baumgartner, Judith,Driess, Matthias
-
supporting information
p. 8840 - 8848
(2015/09/21)
-
- Highly reversible lithium storage in a 3D macroporous Ge@C composite
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A porous Ge@C composite was synthesized by magnesiothermic reduction reaction of GeO2, Mg powder and glucose followed by an etching process with HCl solution. Compared to a porous Ge electrode, the porous Ge@C composite electrode delivers better cycling stability (~100% capacity retention after 100 cycles at the 0.2 C rate) and higher rate capability (440 mA h g-1 at 1800 mA g-1). The improved electrochemical performance results from the synergistic effect of the 3D interconnected porous structure and the carbon shells. The local pores could buffer the volume change and the conductive carbon shell could prevent the aggregation of Ge as well as enhance the electronic conductivity of the whole electrode. the Partner Organisations 2014.
- Cheng, Jianxiu,Wang, Jiaqing,Li, Weihan,Liu, Xiaowu,Yu, Yan
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p. 37746 - 37751
(2014/12/09)
-
- Investigation of electrochemical reduction of GeO2 to Ge in molten CaCl2-NaCl
-
Electrochemical reduction of solid GeO2 has been investigated in the mixed CaCl2-NaCl melt at 1023 K for developing a more efficient process for preparation of Ge. Cyclic voltammetry and potentiostatic electrolysis were applied to study the GeO2-loaded metallic cavity electrode. In addition, porous GeO2 pellets were reduced by potentiostatic and constant cell voltage electrolysis with a graphite anode, and the electrolysis products were analyzed by powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry, focusing on understanding the reduction mechanism and the impact of electrode potential on the product purity. It was found that the reduction of GeO2 to Ge occurred at a potential of about -0.50 V (vs. Ag/Ag+), but generating various calcium germanates simultaneously, whose reduction was a little more difficult and needed a potential more negative than -1.00 V. However, if the cathode potential exceeded -1.60 V, Ca (or Na) - Ge intermetallic compounds might form. These results gave an appropriate potential range between -1.10 and -1.40 V for the production of pure germanium. Rapid electrolysis of GeO2 to pure Ge has been realized at a cell voltage of 2.5 V with a current efficiency of about 92%.
- Rong, Liangbin,He, Rui,Wang, Zhiyong,Peng, Junjun,Jin, Xianbo,Chen, George Z.
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p. 352 - 359
(2015/02/02)
-
- Thermal decomposition of tetramethylsilane and tetramethylgermane by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry
-
Thermal decomposition of tetramethylsilane (TMS) and tetramethylgermane (TMG) was studied on a short time scale of 20100 ms using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Primary decomposition of TMS and TMG occurred via loss of a methyl radical to form ?Si(CH3)3 and ?Ge(CH3)3, respectively. Both the ?Si(CH3)3 and ?Ge(CH3)3 radicals underwent secondary loss of a second methyl radical to form :Si(CH3)2 and :Ge(CH3)2, respectively. A previously unobserved secondary decomposition process in TMS involving loss of H atom from ?Si(CH3)3 followed by elimination of H2 to form SiC3H8, SiC3H6, and SiC3H4 was also identified. Sequential loss of the third and fourth methyl radical with significant formation of Ge and Ge2 was observed in the TMG pyrolysis. Loss of a third methyl radical in the TMS pyrolysis was not significant, while Si and SiC products were possibly produced. Secondary reactions of methyl to form unsaturated CxHy species, particularly in the TMG decomposition, were also observed.
- Lemieux, Jessy M.,Zhang, Jingsong
-
-
- Charge and magnetization transport in Cd0.81mn 0.19GeP2 dilute magnetic semiconductor under high pressures
-
Cd0.81Mn0.19GeP2 dilute magnetic semiconductor (DMS) has been subjected to a complex study of electric and magnetic properties under high hydrostatic pressures of up to 7 GPa with pressure rise and release. Electrical resistivity, Hall factor, transverse magnetoresistance, relative magnetic susceptibility, and volume magnetostriction have been measured. Compressibility (k) and spontaneous magnetization coeffi-cient (ωS) have been calculated. Pleiades Publishing, Ltd., 2012.
- Mollaev,Kamilov,Arslanov,Novotortsev,Marenkin,Trukhan,Arslanov,Zalibekov,Fedorchenkob
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p. 987 - 990
(2012/10/08)
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- Hypervalent sulfur-functionalized diphosphagermylene and diphosphastannylene compounds
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The reaction between either GeCl2(1,4-dioxane) or SnCl 2 and 2 equiv of the lithium phosphide [{(Me3Si) 2CH}P(C6H4-2-SMe)]Li(tmeda) gives the corresponding diphosphatetrylenes [{(Me3Si)2CH}P(C 6H4-2-SMe)]2E [E = Ge (10), Sn (11)] in good yields. Both 10 and 11 crystallize as discrete monomers in which the Ge and Sn atoms are coordinated by both P and S atoms. Although 10 and 11 crystallize as racemic mixtures of the RR and SS diastereomers, variable-temperature NMR experiments suggest that, in solution, these compounds are in dynamic equilibrium with small amounts of the corresponding RS and SR diastereomers. DFT calculations reveal that the lowest-energy minima for both 10 and 11 possess rac stereochemistry; two higher-energy minima were located for each of 10 and 11, both of which have meso stereochemistry. The two calculated meso diastereomers differ in the location of the sulfur and phosphorus substituents within the pseudo-trigonalbipyramidal structures. Both 10 and 11 decompose on exposure to light, generating the diphosphine {(Me3Si) 2CH}(C6H4-2-SMe)P-P(C6H 4-2-SMe){CH(SiMe3)2} (14) as the major product.
- Izod, Keith,Clark, Ewan R.,Clegg, William,Harrington, Ross W.
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p. 246 - 255
(2012/05/04)
-
- Ge chemical vapor deposition on GaAs for low resistivity contacts
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This paper reports the two-dimensional epitaxial growth of thin intrinsic Ge and in-situ doped n-Ge on GaAs substrates by atmospheric pressure chemical vapor deposition. High quality Ge growth on GaAs is activated almost instantly by an optimized pregrowth procedure. Ga autodoping is found to occur within the first Ge monolayers close to the Ge/GaAs interface. The introduction of high P H3 flows during the Ge growth yields the in-situ n-Ge growth on GaAs with an electrically activated dopant concentration of 3× 1019 cm-3. Additionally, n-Ge selective growth on the source/drain areas of an n-GaAs metal oxide semiconductor structure, followed subsequently by the NiGe formation, has been demonstrated to yield an ohmic contact with a contact resistance of 0.13 ωcm.
- Vincent,Firrincieli,Wang,Waldron,Franquet,Douhard,Vandervorst,Clarysse,Brammertz,Loo,Dekoster,Meuris,Caymax
-
p. H203-H207
(2011/04/15)
-
- Bending of nanowire-flexible substrate assemblies integrated via direct synthesis methods
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Nanowires are successfully synthesized directly onto two types of flexible substrates, Kapton and silicone. Reduced temperature catalyst-assisted chemical vapor deposition techniques enable the direct integration. The mechanical properties of these assemblies are evaluated using bending tests where tensile or compressive strains are applied to the samples. Substrate-dependent nanowire properties, thin film formation, and failure of the integrated assemblies are observed. Image: Failure of a germanium nanowire (GeNW) array synthesized on a flexible substrate once subjected to compressive strains.
- Rodgers, Justin,Edel, Julia,Rivera, Johan,Englander, Ongi
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p. 2443 - 2449
(2011/11/30)
-
- Formation mechanism of self-assembled gesige composite islands
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This study investigated the formation mechanism of GeSiGe composite islands on Si(001) using a combination of selective wet chemical etching, atomic force microscopy and high-resolution transmission electron microscopy. After upper Ge-rich parts were removed by selective etching, the etched GeSiGe composite islands exhibited pyramid structures, which differed from the ring-like isocompositional profiles observed in conventional Ge islands. Experimental results demonstrated that the multilayered GeSiGe composite islands were almost defect-free and suffered from a serious SiGe intermixing during growth. The shape and size distribution of composite islands can be further controlled by tuning the island parameters. We elucidate these phenomena on the basis of low surface diffusivity and strain adjustment of the thin Si layer in composite islands. These composite islands were also found to exhibit an apparent enhancement and blueshift in photoluminescence emission. These results indicated that GeSiGe composite islands would be potentially useful as an optoelectronic material operating in the telecommunication range.
- Lee, Sheng-Wei,Chang, Hung-Tai,Chang, Jeng-Kuei,Cheng, Shao-Liang
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p. H1113-H1116
(2011/12/13)
-
- Controlled synthesis and size-dependent polarization domain structure of colloidal germanium telluride nanocrystals
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Germanium telluride (GeTe) exhibits interesting materials properties, including a reversible amorphous-to-crystalline phase transition and a room-temperature ferroelectric distortion, and has demonstrated potential for nonvolatile memory applications. Here, a colloidal approach to the synthesis of GeTe nanocrystals over a wide range of sizes is demonstrated. These nanocrystals have size distributions of 10-20% and exist in the rhombohedral structure characteristic of the low-temperature polar phase. The production of nanocrystals of widely varying sizes is facilitated by the use of Ge(II) precursors with different reactivities. A transition from a monodomain state to a state with multiple polarization domains is observed with increasing size, leading to the formation of richly faceted nanostructures. These results provide a starting point for deeper investigation into the size-scaling and fundamental nature of polar-ordering and phase-change processes in nanoscale systems.
- Polking, Mark J.,Zheng, Haimei,Ramesh, Ramamoorthy,Alivisatos, A. Paul
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p. 2044 - 2047
(2011/04/12)
-
- Interfacial electrochemistry and electrodeposition from some ionic liquids: In situ scanning tunneling microscopy, plasma electrochemistry, selenium and macroporous materials
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In this paper we report on recent results from our group, namely on the interface ionic liquid/electrode, plasma electrochemistry and electrodeposition of selenium and of macroporous structures. Ionic liquids show an interesting and liquid dependent surface chemistry: in some liquids the long range "herringbone" superstructure of Au(1 1 1) is visible, in others it is not. Glow discharge plasmas can be employed as a contact free electrode to make nanoparticles in solutions, e.g. nanoparticles of germanium. Selenium can be electrodeposited from ionic liquids under environmental conditions in an open cell and both the red and the grey phases of selenium are feasible. With the help of self organized opal structures of polystyrene spheres macroporous materials of Ag, Al and conducting polymers can be made. The prospects and limits of ionic liquids in surface electrochemistry and electrodeposition are shortly discussed.
- Aal, Alsayed Abdel,Al-Salman, Rihab,Al-Zoubi, Mohammad,Borissenko, Natalia,Endres, Frank,H?fft, Oliver,Prowald, Alexandra,Zein El Abedin, Sherif
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p. 10295 - 10305
(2012/01/12)
-
- XAS/EXAFS studies of Ge nanoparticles produced by reaction between Mg 2Ge and GeCl4
-
We present results of an XAS and EXAFS study of the synthesis of Ge nanoparticles formed by a metathesis reaction between Mg2Ge and GeCl4 in diglyme (diethylene glycol dimethyl ether). The progress of the formation reaction and the products formed at various stages in the processing was characterised by TEM and optical spectroscopy as well as in situ XAS/EXAFS studies using specially designed reaction cells.
- Pugsley, Andrew J.,Bull, Craig L.,Sella, Andrea,Sankar, Gopinathan,McMillan, Paul F.
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p. 2345 - 2352
(2011/11/13)
-
- Fabrication of nanometer-scale Si field emitters using self-assembled Ge nanomasks
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Large-area, nanometer-scale Si field emitters have been fabricated by selective chemical etching of self-assembled Ge islands on Si. Taking advantage of the relatively low etching rate, uniform Ge islands act as virtual nanomasks for the underlying Si substrate. During selective chemical etching, Ge nanomasks shrink into small Ge-core islands, which determine the apex sharpness of the resulting Si pyramidal tips. The results demonstrate that Si pyramidal tips exhibited improved antireflective and electron field emission characteristics compared to as-grown Ge islands. The high field enhancement factor can be attributed to high tip density, nanoscale apex, and well-controlled spacing between Si pyramidal tips. This work offers a low cost alternative for designing and fabricating high efficiency Si-based field emitters or nanodevices.
- Lee, Sheng-Wei,Wu, Bo-Lun,Chang, Hung-Tai
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p. H174-H177
(2010/06/12)
-
- Selective area growth of high quality InP on Si (001) substrates
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In this work, we demonstrate the selective area growth of high quality InP layers in submicron trenches on exactly (001) oriented Si substrates by using a thin Ge buffer layer. Antiphase domain boundaries were avoided by annealing at the Ge surface roughening temperature to create additional atomic steps on the Ge buffer layer. The mechanism of Ge surface atomic step formation and the corresponding step density control method are illustrated. The elimination of antiphase boundaries from the optimized Ge buffer layer, together with the defect necking effect, yield defect-free top InP layers inside the trenches.
- Wang,Leys,Loo,Richard,Bender,Waldron,Brammertz,Dekoster,Wang,Seefeldt,Caymax,Heyns
-
-
- PKU-10: A new 3D open-framework germanate with 13-ring channels
-
PKU-10, a germanate with the formula [(CH3)4N] 3Ge11O19(OH)9, is synthesized under hydrothermal conditions, and its structure is determined by single-crystal X-ray diffraction data. PKU-10 possesses 3D intersected 13-ring channels and presents a new 6-connectedness linkage mode of the Ge7 cluster, T 3P2O, forming a pcu topological network. Each Ge 7 cluster is, in fact, surrounded by eight Ge7 clusters in a nearly perfect cube because the hydrogen bonds between Ge7 clusters are also taken into account. The structure-directing agent tetramethylammonium (TMA+) ions, locating in the channels, can be partially exchanged by Li+ with retention of the germanate framework. The germanate framework collapses with decomposition of the TMA+ ions at temperatures higher than 240 °C.
- Su, Jie,Wang, Yingxia,Wang, Zheming,Liao, Fuhui,Lin, Jianhua
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p. 9765 - 9769
(2011/01/10)
-
- The new binary intermetallic YbGe2.83
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The new compound YbGe2.83 was obtained from the reaction of Yb and Ge in liquid indium. The crystal structure of YbGe2.83 adopts the trigonal, P3m1 space group with a=b=8.3657(12) and c=7.0469(14) . The structure of YbGe2.83 is a variant of the CaAl2Si2 structure type with ordered vacancies. Germanium atoms form double layers of puckered hexagons creating slabs that sandwich the Yb atoms. YbGe2.83 can be classified as a Zintl compound with the formula Yb (2x)(Ge2.83)(2x)-. The deficiencies at the Ge sites cause a mixed/intermediate valent state of ytterbium (Yb2.35). Valence bond sum calculations suggest an average valence of Yb ions in YbGe 2.83 of 2.51 consistent with an intermediate valence compound.
- Peter Sebastian,Kanatzidis, Mercouri G.
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p. 2077 - 2081
(2011/01/10)
-
- Thermal, magnetic, electronic, and superconducting properties of rareearth metal pentagermanides REGe5 (RE = La, Nd, Sm, Gd) and synthesis of TbGe5
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A series of isotypic rare-earth metal pentagermanides including the new compound TbGe5 were prepared by high-pressure synthesis. They crystallize in the orthorhombic space group Immm [No. 71; a = 395.70(9) pm; b = 611.1(2) pm, and c = 983.6(3) pm for TbGe5]. The crystal structure is isotypic to LaGe5 and consists of puckered germanium slabs, which sandwich, a second germanium species and the rare-earth metal atoms. At ambient pressure, the thermal, decomposition of the phases REGe5 (RE = La, Nd, Sm, Gd, and Tb) proceeds via discrete intermediate steps into Ge(cF8) and thermodynamically stable germanium-poorer phases. The investigated com-pounds REGe5 are paramagnetic metallic conductors, which order antiferromagnetically at low temperatures. Specific heat measurements reveal that the superconducting state of LaGe5 below Tc = 7.1(1) K is characterized by a critical field of μ0Hc2 = 0.2 T and weak electronphonon coupling. Density-functional based band-structure calculations yield a very similar electronic structure for all the isotypic REGe5 compounds. Besides a slight increase in the width of the valence band for smaller RE atoms, only minor differences are found for the two different germanium environments.
- Meier, Katrin,Cardoso-Gil, Raul,Schnelle, Walter,Rosner, Helge,Burkhardt, Ulrich,Schwarz, Ulrich
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p. 1466 - 1473
(2011/01/09)
-
- Deposition of germanium nanowires from hexamethyldigermane: Influence of the substrate pretreatment
-
Germanium nanowires (GeNWs) were synthesized by low pressure chemical vapor deposition of hexamethyldigermane (GeMe3)2 at 490°C and a pressure of 90-100 Pa. GeNWs of several nanometers in diameter and a few micrometers in length were deposited onto substrates made of stainless steel, Fe, Mo, Ta, W, Si, and SiO2. The influence of surface pretreatment of the substrates (roughening of surface, grooves made by a diamond tip or Ge thermal evaporation) is discussed. GeNW deposits were studied using scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, Raman spectroscopy, and energy-dispersive X-ray analyses.
- Dinek,Fajgar,Klementova,Subrt
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p. K218-K222
(2011/01/06)
-
- Solid phase epitaxy of amorphous Ge on Si in N2 atmosphere
-
We demonstrate a straightforward and economical way to obtain smooth germanium layers of high quality on silicon. Thin amorphous germanium layers deposited by plasma enhanced chemical vapor deposition on Si(111) substrates are transformed into single crys
- Lieten,Degroote,Leys,Posthuma,Borghs
-
-
- Shape-and dimension-controlled single-crystalline silicon and sige nanotubes: Toward nanofluidic fet devices
-
We report here on the formation of robust and entirely hollow single-crystalline silicon nanotubes, from various tubular to conical structures, with uniform and well-controlled inner diameter, ranging from as small as 1.5 up to 500 nm, and controllable wa
- Ishai, Moshit Ben,Patolsky, Fernando
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p. 3679 - 3689
(2009/08/07)
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- Nanocomposite of amorphous Ge and Sn nanoparticles as an anode material for Li secondary battery
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Nanocomposites of amorphous Ge and Sn nanoparticles are prepared from the vacuum annealing of the butyl-capped Ge gels and Sn P0.94 nanoparticles at 400°C for 7 h, and their electrochemical properties and nanostructure changes are investigated during electrochemical cycling. The nanocomposite displays a first charge capacity of 1078 mAhg with a capacity retention of 64% after 50 cycles. However, both individual Ge and Sn nanoparticles display rapid capacity fade, showing 20% capacity retention after 50 cycles. A superior electrochemical property of the nanocomposite to the Sn and Ge nanoparticles is believed to be related to the fact that the amorphous Ge phase acts as an intergrain electrical connecter when Sn particles are pulverized.
- Kim, Min Gyu,Cho, Jaephil
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p. A277-A282
(2009/05/15)
-
- Synthesis and characterization of germanium coordination compounds for production of germanium nanomaterials
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A series of novel germanium(II) precursors was synthesized to initiate an investigation between the precursors' structures and the morphologies of the resulting nanoparticles. The precursors were synthesized from the reaction of Ge[N(SiMe3)sub
- Boyle, Timothy J.,Tribby, Louis J.,Ottley, Leigh Anna M.,Han, Sang M.
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p. 5550 - 5560
(2010/06/15)
-
- The impacts of surface conditions on the vapor-liquid-solid growth of germanium nanowires on Si (100) substrate
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The impacts of surface conditions on the growth of Ge nanowires on a Si (100) substrate are discussed in detail. On Si O2 -terminated Si substrates, high-density Ge nanowires can be easily grown. However, on H-terminated Si substrates, growing Ge nanowires is more complex. The silicon migration and the formation of a native Si O2 overlayer on a catalyst surface retard the growth of Ge nanowires. After removing this overlayer in the HF solution, high-density and well-ordered Ge nanowires are grown. Ge nanowires cross vertically and form two sets of parallel nanowires. It is found that nanowires grew along 〈110〉 directions.
- Li,Usami,Muraki,Mizuta,Odal
-
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- Preparation of freestanding germanium nanocrystals by ultrasonic aerosol pyrolysis
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This letter reports a synthetic route adaptable for the continuous, large-scale production of germanium (Ge) nanocrystals for emerging electronic and optoelectronic applications. Using an ultrasonic aerosol pyrolysis approach, diamond cubic Ge nanocrystals with dense, spherical morphologies and sizes ranging from 3 to 14 nm are synthesized at 700 °C from an ultrasonically generated aerosol of tetrapropylgermane (TPG) precursor and toluene solvent. The ultimate crystal size demonstrates a near linear relationship within the range of TPG concentrations investigated, while the shape of the measured size distributions predicts multiple particle formation mechanisms during aerosol decomposition and condensation.
- Stoldt, Conrad R.,Haag, Michael A.,Larsen, Brian A.
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- A cyclopentadienide analogue containing divalent germanium and a heavy cyclobutadiene-like dianion with an unusual Ge4 core
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The first isolable cyclogermylidenide salt 2 has been synthesized and isolated by facile dehalogenation of the N-heterocyclic chlorogermylene 1 with elemental potassium in ether and isolated in the form of yellow crystals in 33% yield. Single-crystal X-ray diffraction analysis revealed that 2 crystallizes as a dimeric half-sandwich complex of aromatic C3NGe rings interconnected via intermolecular Ge(II)→K dative bonds. Its yield can be improved up to 42% by gentle reduction of 1 (or its related GeCl3 complex 8) using potassium graphite. Additionally, the remarkable K2Ge4 cluster compound 9 has been isolated as a side product which consists of an unusual dianionic Ge4 core with parallelogram configuration and pronounced aromaticity as indicated by highly negative NICS values. Copyright
- Wang, Wenyuan,Yao, Shenglai,Van Wuellen, Christoph,Driess, Matthias
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p. 9640 - 9641
(2009/02/04)
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- Alkyl-terminated crystalline Ge nanoparticles prepared from NaGe: Synthesis, functionalization and optical properties
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High purity NaGe was directly prepared by a low-temperature reaction of NaH and Ge. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. This material is a useful starting reagent for the preparation of Ge nanoparticles. Hydrogen-terminated germanium (Ge) nanoparticles were prepared by reaction of NaGe with NH4Br. These Ge nanoparticles could be prepared as amorphous or crystalline nanoparticles in quantitative yields and with a narrow size distribution. The nanoparticles were functionalized via thermally initiated hydrogermylation with 1-eicosyne, CH3(CH2)17C≡CH to produce alkyl-terminated Ge nanoparticles. The modified Ge nanoparticles were characterized by powder XRD, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and Raman spectroscopy, and photoluminescence (PL) spectroscopy. The alkyl-functionalized Ge nanoparticles can be expected to have promising applications in many technological and biological areas.
- Ma, Xuchu,Wu, Fengyi,Kauzlarich, Susan M.
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p. 1628 - 1633
(2009/02/02)
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- Infrared spectra, structure, and bonding of the GeH3-CrH, HGe≡MoH3, and HGe≡WH3 molecules in solid neon and argon
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Laser ablated chromium, molybdenum, and tungsten atoms react with germane during condensation in excess noble gases. The chromium reaction stopped at the germyl metal hydride, molybdenum gave some hydride but mostly germylidyne, and tungsten reacted spontaneously to give only the germylidyne species. These molecules were identified by isotopic shifts, density-functional theory product energy and frequency calculations, and comparison to the analogous methane and silane reaction products. Effective bond orders for the HGe≡MoH 3 and HGe≡WH3 molecules are 2.82 and 2.87 using the B3LYP density functional, and are slightly lower than their silicon and carbon analogues. Our calculated Ge≡M triple bond lengths for these simple trihydride complexes are 0.05 to 0.10 A shorter than those measured for larger group 6 organometallic complexes.
- Wang, Xuefeng,Andrews, Lester
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p. 8159 - 8166
(2009/03/11)
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