Metallic Arsenic Research Articles

The As-terminated Si(001) surface and its oxidation in molecular oxygen: an Si 2p and As 3d core-level study with synchrotron radiation

The strong resistance of the As-terminated Si(001) surface to oxidation in molecular oxygen at room temperature is the subject of this study. As 3d and Si 2p photoemission spectra, as well as valence band spectra, excited with synchrotron radiation (135 eV ≤ hv ≤ 165 eV), have been recorded as a function of increasing O 2 exposures, over the range 2400–1.4 × 10 13 L (langmuir). Spectral changes, simultaneously observed in the As 3d and Si 2p core-levels near ∼ 10 12 L are indicative of the onset of oxidation. However a modification of the valence band, due to the contribution of O 2p states, is clearly evident from ∼ 10 11 L, pointing to the presence of weakly bound oxygen species at that exposure. These results are confronted with a previous Auger study reporting an oxygen saturation coverage (0.5 monolayer) already in the 400–2000 L range, interpreted as the insertion of an oxygen atom between two dimerized arsenic atoms. On the contrary our data show that surface oxidation is a slow process, spatially inhomogeneous, as some dimerized As remain intact (∼ 24%) up to exposures as large as ∼ 10 13 L. Oxidation is not limited to the outermost layer, as three arsenic oxidation states and the four silicon oxidation states (indicative of subsurface oxidation) are detected simultaneously. Moreover metallic arsenic shows up: this suggests a reduction of the arsenic oxide by silicon. Arsenic losses are also observed, probably via sublimation of As 4O 6 molecules.

Speciation of arsenic in the atmosphere

In this paper is presented a study of speciation of arsenic in air, consisting in the separation and determination of arsine, metallic arsenic, inorganic trivalent and pentavalent arsenic, organic monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and/or their salts. These arsenic compounds are the most common found in air and are characterised by different toxicities. The proposed procedure is based on a sequential sampling where, first, the air is filtered on a cellulose membrane to collect the particulate matter, then it is purged into proper solutions able to stop the arsenic species present in the vapour state, except arsine. This latter compound is retained in an oxidising solution of permanganate as arsenate. The determination of the different species of arsenic in the particulate and in the vapour phase is described as well the typical interferences that can be encountered either in the solubilization procedure or in the analytical measurements: in many cases suggestions are proposed in orde...

古河機械金属（株）における高純度金属ひ素について

High purity metallic arsenic is produced through a process consisting of the chlorination of arsenious acid (As2O3), distillation and then hydrogen reduction.We combine these methods in order to produce 6N-7N5 metallic arsenic.The purity is confirmed by analytical methods such as Emission Spectrographic, SSMS and GDMS.High purity metallic arsenic is used for gallium arsenide (III-V compounds) and arsenic selenide (chalcogenide glass). Gallium arsenide-based devices are developed and manufactured for communications and computing machines. Chaicogenide glass is used in the photoconductor such as a copy machine.High purity metallic arsenic is used for gallium arsenide (III-V compounds) and arsenic selenide (chalcogenide glass). Gallium arsenide-based devices are developed and manufactured for communications and computing machines.Chaicogenide glass is used in the photoconductor such as a copy machine.Investigations on the properties of arsenic compounds such as arsine, arsenious acid and arsenic chloride have made it possible to prepare a high purity arsenic in safety.

Industries using arsenic and arsenic compounds

AbstractThis paper reviews industries using arsenic and arsenic compounds such as wood preservatives and agricultural chemicals, the use of arsenic trioxide in glass manufacture, and the applications of metallic arsenic in non‐ferrous alloys and of high‐purity arsenic in the electronics industry.

Korringa and phonon nuclear-spin-lattice relaxation in metallic arsenic.

The spin-lattice relaxation time (${\mathit{T}}_{1}$) in arsenic ${(}^{75}$As nucleus; I=3/2) has been measured, using pulsed nuclear-quadrupole-resonance methods, as a function of temperature from 4 to 596 K. The results show that ${\mathit{T}}_{1}$ follows the Korringa relation (${\mathit{T}}_{1}$T=const) for temperatures below the Debye temperature (${\mathit{FTHETA}}_{\mathit{D}}$=282 K). Above ${\mathit{FTHETA}}_{\mathit{D}}$ the data break away from this relation, and the measured ${\mathit{T}}_{1}$ is shorter than that predicted by a nucleus-carrier relaxation model. Previous calculations of nucleus-carrier spin-flip transition probabilities involving a spherical Fermi surface (FS) have been extended to the nonspherical FS of arsenic. Modified expressions have been derived using a spheroidal approximation to the FS pockets. The carrier wave functions are approximated by free-atom wave functions. These calculations can account for the magnitude of measured nucleus-carrier interactions at low temperatures, and predict the usual Korringa law for the temperature dependence. The experimental results above ${\mathit{FTHETA}}_{\mathit{D}}$ can be accounted for using both nucleus-carrier processes (\ensuremath{\propto}T) and nucleus-phonon processes (\ensuremath{\propto}${\mathit{T}}^{2}$).

XPS-Analysis of Ion-Beam-Induced Oxidation (IBO) of AlxGa1−xAs Substrates

ABSTRACTXPS analysis was used to characterise GaAs, Al0.4Ga0.6As and Al0.8Ga0.2As targets bombarded with an O2+ beam ranging from 1 keV to 5 keV. The bombardments were carried out at different angles of incidence from 0° to 60°. In all cases a strong preferential sputtering of arsenic gives rise to an As-depleted altered layer, formed by a mixture of gallium, arsenic and aluminium oxides with metallic gallium and arsenic. Aluminium and gallium are preferentially oxidized, a fact that correlates with the corresponding heat of formation of the oxides, whereas the arsenic oxidation requires a minimum incorporation of oxygen into the matrix. For all experimental conditions a considerably lower oxidation level has been observed in every case as compared to the IBO of silicon.

MOVPE growth of GaAs using metallic arsenic and trimethylgallium

GaAs homoepitaxial layers were grown using trimethylgallium (TMG) and metallic arsenic as a source material for metalorganic vapor phase epitaxy (MOVPE). p-Type GaAs layer was obtained with a growth rate of 3–8nm/s. The full width at half-maximum (FWHM) of double-crystal X-ray diffraction was found to be comparable to that of bulk GaAs (0.015°) when TMG concentration is less than 3.3×10 -4 mol/ m 3. Further increase of TMG concentration resulted in the increase of FWHM. Carrier concentration of (-4)×10 16 cm -3 and Hall mobility of 203–348 cm 2/V.s were obtained at a substrate temperature of 650°C, V/III ratio of 29 and total pressure of 1.3×10 4 Pa. Methyl radical (CH 3), methane-d 0 (CH 4) and methane-d 1 (CH 3D) were found to be formed by mass spectroscopy using D 2 as replacement of H 2. The formation of CH 3D is explained by the reaction of CH 3 with D 2. CH 4 is produced directly by the decomposition of TMG and/or produced by the reaction of CH 3 with CH 3.

Ion beam oxidation of GaAs: The role of ion energy

In this work, room temperature oxidation of GaAs was investigated using ion beam oxidation (IBO). In IBO, an ion beam is used to introduce oxygen athermally into the substrate, in this case GaAs. GaAs bonds are broken upon collision with the ions, making gallium and arsenic atoms readily available to react with the oxygen species. Ion beam oxidation of GaAs at room temperature was studied as a function of oxygen ion energy between 500 and 8 keV. The ion beam oxidized GaAs was characterized in situ by Auger electron spectroscopy (AES) and ex situ with x-ray photoelectron spectroscopy (XPS) for accurate determination of the film chemical composition. Below 1 keV, a thin oxide film is formed: it is composed of Ga2O3 and As2O3 with almost no metallic arsenic, and presents insulating properties. As the ion energy increases, preferential sputtering of As and decomposition of As2O3 increase and prevent formation of an insulating film. No damage was detected by Rutherford backscattering spectrometry (RBS) combined with ion channeling, in the substrate subjected to IBO below 1 keV.

Investigation of low growth temperature AlGaAs and GaAs using metal–insulator–semiconductor diagnostic structures

GaAs and Al0.3Ga0.7As layers grown by molecular-beam epitaxy (MBE) at 250 °C and incorporated as the gate insulators in metal–insulator–semiconductor (MIS) structures are examined using capacitance–voltage and current–voltage techniques. Samples which are not annealed, and samples annealed for 10 and 20 min under an arsenic ambient at 600 °C are examined. MIS structures using material grown at low temperatures without annealing are found to be extremely leaky at room temperature due to a high defect concentration. For unannealed samples and samples annealed for 10 min, a deep level trap is found to be the source of free carriers in the low growth temperature layer. Capacitance–voltage profiling can be accomplished on both structures, indicating the Fermi level is weakly pinned in these structures. For samples annealed for 20 min, however, no modulation of the device capacitance is possible, and the layer exhibits extremely high resistivity. This indicates that the Fermi level is pinned strongly in samples annealed for 20 min, possibly due to the precipitation and/or interfacial segregation of metallic arsenic.

ヒ素の電着とヒ素電着膜の電気化学的挙動

Electrodeposition of arsenic has been studied in acidic and alkaline solutions containing As2O3. The current efficiency from the electrodeposition of arsenic was approximately 90% in initial 3 hours but it gradually falled down below 50% after 20 hours. The cathode deposits were metallic grey arsenic at low current densities but was less-conductive powdery arsenic at high current densities. An X-ray analysis indicated that the deposits were non-crystalline. Cathodic hydrogen evolution on the electrodeposited arsenic in an acidic solution obeyed the Tafel relation with a slope of 0.12V/decade in a limited range of current densities and the exchange current density for hydrogen was in the order of 10-3 A m-2. It was also found that the arsenic electrode was slowly reduced to arsine (AsH3) during the cathodic polarization experiment. The anodic polarization curves for the arsenic exhibited a Tafel line with a slope of 0.06V/decade.

TDPAC Measurement of the quadrupole interaction of77Se in arsenic

By TDPAC the quadrupole coupling constant for77Se (5/2−, 248 keV, 9.3 ns) in metallic arsenic was measured to be υQ = 700 ± 60 MHz. The tabulation of electric field gradients (EFGs) for some different sp impurity host combinations shows large values for impurities with 6 valence electrons. If we assume that the selenium impurity is substituted in arsenic, then it is possible to interpret the very high υQ by the assumption of a big EFG and a large quadrupole moment (approximately 1 b) of the excited77Se nucleus.

Atom formation mechanisms of As with different techniques in atomic absorption spectroscopy

In this work, the atomization mechanism of As in flameless atomic absorption spectroscopy is investigated with both direct injection of the analyte into the furnace and with the well-known hydride generation method. The proposed mechanisms are controlled by the variation of the obtained signals with various pre-heating programmes of the furnace. In the direct injection method, it is found that arsenic is vaporized to AsO and atomized by the dissociation of the oxide. In the hydride generation technique however, the formed AsH 3 is decomposed on the graphite surface before the atomization temperature is reached and the metallic arsenic is vaporized as As 4, which is then decomposed to As 2 dimers and atomized by gas-phase dissociation.

Identification of Arsenic Surface Species on the Si (100) Surface

ABSTRACTThe molecular character of arsenic adsorbed on the Si (100) surface has been investigated using thermal desorption spectroscopy (TDS) and Auger electron spectroscopy (AES). A variety of arsenic surface species were deposited on the silicon surface by employing different evaporation sources, including metallic arsenic, arsine gas, and chips of GaAs crystals. We present coverage dependent spectra showing the desorption of As4 tetramers at 350°C and As2 dimers at 900°C. The loosely bound arsenic is adsorbed from the solid evaporation sources only and resides on the surface as tetramers. The tightly bound arsenic does not form multiple layers and the high desorption temperatures suggests the adsorbed arsenic exists as monomers.

Activity of arsenic in copper

Values have been reported in the literature for the Henrian activity coefficient for arsenic in molten copper ranging from 1.45 × 10-4 to 5 × 10-7 at temperatures between 1273 and 1573 K. In this study, that data was reexamined and was found to be in closer agreement than originally reported. The Henrian activity coefficient was found to range from 2.2 × 10-3 at 1273 K to 5.6 × 10-3 at 1373 K. The experimental data indicate that at 0.21 < NAs < 0.30 the activity coefficient γAs can be determined from the following equations: log γAs = -5.58 NCu2+ 1.65(T = 1273 K) log γas = -6.22 NCu/2+ 2.25(T = 1373 K) This study also examined the extent of the disassociation of tetratomic arsenic vapor as As, As2 and As3. The results of the analysis indicate that As2 is the predominant species when arsenic vapor, equilibrated with metallic arsenic at temperatures below 873 K, is heated to temperatures above 1273 K.

Zeeman effect and level identification of As i

The Zeeman effect of the neutral arsenic spectrum was observed photographically from 1937 to 11 244 Å. Well-defined Zeeman patterns of 130 As i lines were recorded and yielded 61 Landé g values of which 9 were previously available. The light source was an electrodeless lamp of quartz containing metallic arsenic and helium carrier gas at 3–5 Torr; it was operated in a magnetic field of 24 025 or 10 000 G and excited by a standard microwave generator. Conditions that were favorable for the excitation of the first spectrum of arsenic were noted and characterized. The J and g values obtained from our Zeeman patterns confirmed most of the existing As i analysis but forced reclassification of several terms. There is acceptable agreement between the g values and those calculated from intermediate-coupling wave functions obtained by the least-squares fitting of energy levels for the single configuration approximation to 4s2 4p3 and 4s2 4p2 5s. Also, adequate fits of energy levels could be obtained in the single configuration approximation for each of the 4s2 4p2 5p and 4s2 4p2 6p configurations, but large discrepancies occurred in the g values. Such discrepancies were reduced considerably when configuration interaction was included in the calculations, providing positive evidence of configuration mixing that led to the reclassification of several energy levels and to the addition of some of the missing classifications.

Thermal decomposition kinetics of AsF5-doped polyacetylene in vacuum

Electrical conductivity measurements, mass spectra of desorbing species, and ESCA surface analysis are reported for AsF5-doped polyacetylene heated between 50 and 130 °C in vacuum. All measurements indicate first-order decomposition kinetics with activation energies between 13 and 20 kcal mole−1. Decomposition leads to the desorption of AsF3 and F2. Metallic arsenic remains in the polyacetylene as a decomposition by-product.

Neutron activation analysis of arsenic in rocks and sediments by direct evolution with chloride- and bromide-condensed phosphoric acid reagents

A simple method is presented for the determination of arsenic in rocks and in sediments by neutron activation. After irradiating a sample it is, without any other treatment, directly heated in condensed phosphoric acid containing sodium chloride or sodium bromide to evolve arsenic as arsenic(III) chloride or bromide. The distillate is absorbed in distilled water, in which arsenic is later precipitated in elementary form by adding hypophosphite to the solution. From arsenite, arsenic(III) oxide, arsenate and arsenic(III) sulphide, arsenic chloride can be evolved with NaCl-CPA reagent, but elementary arsenic and arsenic(V) oxide do not react with it. However, metallic arsenic is found to react with KIO3-NaCl-CPA and arsenic(V) oxide with the NaBr-CPA, both both evolving arsenic(III) chloride or bromide. Therefore, successive distillations, the first with NaCl-CPA and the second with NaBr-CPA, give a satisfactory means of differential determination of arsenic(III) and arsenate as well as arsenic(V) oxide. For the elementary arsenic a problem still now remains. The chemical recovery of carrier goes well beyond 95%.

Nuclear quadropole resonance in arsenic and bismuth metal

Nuclear quadrupole resonance of 75As and 209Bi have been observed in metallic arsenic and bismuth respectively. The quadrupole constant for 75As extrapolated to 0 K was 47.360 MHz, in good agreement with the value deduced from low-temperature specific heat measurements. The quadrupole coupling constant for 209Bi was 51.2 MHz at 195 K, in agreement with the value deduced from the high-field NMR spectrum.

The structures of orthorhombic and vitreous arsenic

Abstract The structure of the orthorhombic crystal modification of arsenic has been determined from an analysis of X-ray powder diffraction data. The structure is confirmed as being similar to that of black phosphorus, with space group Bmab and eight atoms per unit cell. Each atom is covalently bonded to three neighbours, with two bonds in an ab plane, of length 2·49 A, making an angle of 94·1° and the third bond, of length 2·48 A, at an angle of 98·5° with each of the other two. The structure differs significantly from that deduced from the black phosphorus structure by a simple scaling with bond lengths. The relationship of the glass structure with the structures of both orthorhombic and rhombohedral (metallic) arsenic has been considered. The structure of the vitreous phase is much closer to that of the orthorhombic crystal. A good description of the glass structure may be obtained using a quasi-crystalline model based on this structure with some expansion of the interlayer spacing and some additional ...

Kinetic Studies of Hydrogen Reduction of Arsenic(III) Chloride

The hydrogen reduction of AsC13 to metallic arsenic have been studied kinetically. Under a dynamic flow condition, AsCls was passed through the reactor, and the HCI gas, formed by the 2AsCls+3H2---1/2 Asl3+6HCl reaction, was determined by pH measurement after solidifying unreacted AsC13 in a trap cooled with solid CO2 and alcohol.The rate of formation of arsenic was calculated from the amount of formed HCI gas within unit time.. The apparent activation energy of this reaction was found to be 21.7 kcal/mol at 546-672C, or 38.2 kcal/mol at 672-795C.The percentage of conversion of AsC13 was calculated from thermodynamic equilibrium of the hydrogen reduction. The experimental results agreed approximately with the calculated values when the temperature of the reactor was kept at 850C and mole ratio of AsCl3 to H2 was 1: 3.The relationship between the percentage of deposition of arsenic in the presence of H2 and the temperaturp of arsenic depositing part ef the reaetor was clarified thcoretically, as the temperature affected seriously on the grewth of crystalline arsenic.In practice, it is preferable to keep the temperature of reaction part of the reactor at 850C, and mole ratio of AsCl3 to H2 was 1: 3.0-4.5 and the temperature of atsenic depositing part at 350-400C.