Arsine Research Articles

Ultraviolet and infrared absorption spectra of promising organoarsine photochemical vapor deposition reagents

Ultraviolet and infrared absorption spectra were recorded for two monoalkylarsines, tertiarybutylarsine and monoethylarsine, and their ultraviolet absorption cross sections were determined. Both tertiarybutylarsine and monoethylarsine absorb strongly in the ultraviolet spectral region, with an absorption maximum found at 189 nm for tertiarybutylarsine, and a maximum for monoethylarsine determined to be < 183 nm. The room temperature absorption cross-section for tertiarybutylarsine at 193 nm (ArF excimer laser wavelength) was found to be 2.6 x 10 -17 cm 2, which is similar to that of trimethygallium. The 193 nm absorption cross section for monoethylarsine was determined to be 1.6 x 10 -17 cm 2. The appreciable ultraviolet absorption cross sections for both of these monoalkylarsines, combined with their enhanced safety relative to arsine, make these species promising reagents for use in photochemically-enhanced vapor deposition reactions of GaAs and related compounds. Furthermore, photodecomposition of these reagents should generate arsenic hydride radicals, which in turn should aid in the growth of high purity GaAs. Characteristic infrared absorption peaks for the hydride and organic moieties of each compound have also been identified for use in diagnostic studies.

AT&T reports arsine emission from MBE chambers

AT&T reports arsine emission from MBE chambers

Reactions of CF 3NO and (CF 3) 2NO with inorganic hydrides

Reactions of CF 3NO and (CF 3) 2NO with hydrides of phosphorus, arsenic and germanium have in some cases led to interesting and novel unsaturated compounds containing PN, AsN and GeN double bonds. Chemical and spectroscopic methods of characterising them will be discussed. Extending the reactions to metal cluster hydrides afforded new cluster derivatives. The (CF 3) 2NO ligand exhibit hindered rotation as displayed by the 19F NMR and supported by x-ray diffraction data.

Interaction of hydrogen at GaAs(100) surfaces

Abstract The interaction of hydrogen at GaAs(100) surfaces has been studied at 300 and 200 K by means of high-resolution electron energy-loss spectroscopy (HREELS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Sample cleaning was done by Ne + ion bombardment (500 eV) and annealing up to 800 K. As a function of hydrogen exposure, in a first stage atomic hydrogen chemisorbs by saturating surface atom dangling bonds. In a second step surface bonds are broken and a change of the geometrical structure results. Finally, higher hydrogen exposures are able to etch GaAs. At room temperature, with increasing hydrogen exposure always a decrease of the concentration of arsenic hydrides occurs relative to that of gallium hydrides, a conclusion drawn from the intensity behaviour of the As-H and Ga-H stretching vibrations. Simultaneously, we observed structure changes from c(8 × 2) or 4 × 6 to 4 × 1, 1 × 1, and 1 × 2. At lower temperatures (200 K) , the arsenic hydrides are more stable than at 300 K. Our results can be interpreted in terms of dimerization, bond breaking, surface diffusion and eventually roughening.

Interaction of hydrogen at GaAs(100) surfaces

The interaction of hydrogen at GaAs(100) surfaces has been studied at 300 and 200 K by means of high-resolution electron energy-loss spectroscopy (HREELS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Sample cleaning was done by Ne+ ion bombardment (500 eV) and annealing up to 800 K. As a function of hydrogen exposure, in a first stage atomic hydrogen chemisorbs by saturating surface atom dangling bonds. In a second step surface bonds are broken and a change of the geometrical structure results. Finally, higher hydrogen exposures are able to etch GaAs. At room temperature, with increasing hydrogen exposure always a decrease of the concentration of arsenic hydrides occurs relative to that of gallium hydrides, a conclusion drawn from the intensity behaviour of the As-H and Ga-H stretching vibrations. Simultaneously, we observed structure changes from c(8 × 2) or 4 × 6 to 4 × 1, 1 × 1, and 1 × 2. At lower temperatures (200 K) , the arsenic hydrides are more stable than at 300 K. Our results can be interpreted in terms of dimerization, bond breaking, surface diffusion and eventually roughening.

Hydrogen induced structure changes of GaAs(1 0 0) surfaces

The interaction of hydrogen with GaAs(1 0 0) surfaces has been studied at room temperature by means of high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron-diffraction (LEED), and Auger electron spectroscopy (AES). Sample cleaning by Ne+ ion bombardment (500 eV) and annealing resulted (with increasing temperatures) in “1 × 1”, 1 × 6, 4 × 1, 4 × 6 and c(8 × 2) LEED structures. As a function of hydrogen exposure, the intensity ratio of the stretching vibrations (As-H/Ga-H) is shown to be characteristic for the specific reconstructed surface. In particular the arsenic hydride concentration gradually decreased in all cases. In addition, an initial weakening of the fractional order LEED spots occurred with increasing hydrogen exposures. Finally, a strong 1 × 2 structure was observed independent of the reconstruction we started with. Simultaneously, a shift of the energetic position of the Ga-H stretching vibration occurred.

Wide area windowless disk plasma lamp of uniform intensity for use in microelectronic film processing

A wide area windowless plasma disk excited by a soft vacuum electron beam provides a wide area uniform source of vacuum ultraviolet (VUV) photons as well as atomic radicals. Hydrogen and oxygen when excited by the soft vacuum electron beam, emit strong atomic resonance radiation at 121.6 and 130 nm, respectively; in fact up to 8% of the total applied discharge power is emitted as VUV photons. The spatial uniformity of the atomic VUV resonance radiation approaches 6% across a disk 19 cm in diameter. The density of atomic oxygen species generated in the plasma disk has also been experimentally determined using an established polymer film etch rate method as well as with a conventional silver thin film sensor. We employ the disk plasma in a windowless configuration to achieve lower temperature chemical vapor deposition (CVD) than conventional thermal CVD. The VUV photon flux as well as the radical and excited atomic gas species emitted from the lamp can assist dissociation of feedstock reactant gases as well as assist heterogeneous surface reactions and increase surface mobility of absorbed species allowing for lower temperature CVD. Thin films of an aluminum nitride and hydrogenated amorphous silicon have been deposited at temperature between 100–400 °C. The deposited films show improvement over other plasma and photo-assisted CVD processes in the film quality achieved, the area covered, the substrate temperature required, and the maximum deposition rates that are possible. In situ generation of arsine (AH3) and unsaturated arsenic hydrides AsHx (x≤2) have also been achieved by placing elemental arsenic in an environment rich in atomic hydrogen created from the disk–plasma source.

A Study of Hydrogen Atom Adsorption on Gallium Arsenide (100) by Multiple Internal Reflection Infrared Spectroscopy

ABSTRACTWe have studied the adsorption of hydrogen atoms on GaAs (100) by multiple internal reflection infrared spectroscopy. The crystal was etched in 1:1:10 H3PO4/H2O2-/H2O solution and in 1:1 HCI/H2O solution, then annealed to 580°C in the vacuum chamber. Hydrogen adsorption was carried out at -90 and 45°C. At both temperatures, a monolayer forms giving rise to infrared bands for arsenic hydride and gallium hydride at 2105 and 1860 cm−1, respectively. The arsenic hydride vibration is polarized parallel to the surface, whereas the gallium hydride vibration is polarized normal to the surface. By monitoring the changes in the intensity of the infrared absorption bands with time during exposure to H atoms and during heating, the kinetics of hydrogen adsorption and desorption can be measured. At -90°C, the H atom sticking probability follows the Langmuir model, S/So = (1-θH). Upon heating the crystal, the arsenic hydride rapidly decomposes near 120°C, while the gallium hydride slowly decomposes between 150 and 400°C.

H atom reactions with GaAs 〈001〉

A GaAs 〈001〉 crystal at room temperature has been exposed to a flux of hydrogen atoms with and without simultaneous 2-keV argon ion bombardment. A modulated molecular beam mass spectrometric detection system is used to monitor the volatile products evolved from the surface, and in situ Auger electron spectroscopy is used to monitor the surface conditions. With the H atom flux alone no volatile products were observed but an arsenic deficiency was seen with Auger electron spectroscopy. With simultaneous H atom exposure and Ar+ bombardment, arsenic hydrides were observed with the mass spectrometer and a larger arsenic deficiency was observed on the processed surface. No gallium hydrides were observed at any time.

Carbon reduction in triethylarsenic-grown GaAs films using chemically activated arsine as a co-reagent

N-type gallium arsenide films grown from triethylarsenic (Et3As) and trimethylgallium (Me3Ga) are generally of poor quality (μ77K(max) = 16,100 cm2/V-s) and are severely contaminated with carbon (>1018 cm−3), whereas films grown using a mixture of triethylarsenic and arsine (AsH3) with Me3Ga are typically of high purity (β77K(max) = 60,000 cm2/V-s) and contain significantly reduced carbon levels (~mid-1015 cm-3). These differences in film purity are due to the inherent growth chemistry of each reagent mixture. The respective growth chemistries of these reagent systems have been inferred from a series of decomposition experiments carried out under pseudo-growth conditions, and the differences in growth chemistry are consistent with the differences in corresponding epilayer purity. Triethylarsenic appears to decompose primarily via a bond homolysis reaction to generate alkyl-containing radical species, which can react with a growing GaAs epilayer to cause severe carbon contamination. In the Et3As/AsH3 coreagent system, the Et3As reagent decomposes to produce these alkyl-containing radical intermediates, but they then apparently react further with the arsine co-reagent to generate reactive arsenic hydride radicals under relatively facile conditions. These reactive arsenic-hydride radical species can contribute to the GaAs growth process without introducing carbon into the resultant films.

Synthesis of allyl dichlorophosphines and arsines, precursors of transient 1-phosphadiene and 1-arsadiene.

O-Silylated dienolates react with PCl3 and AsCl 3 to give the corresponding allyl dichlorophosphines or arsines which are deshydrohalogenated to 1-phospha or arsadiene.

In-Situ Ftir and Mass Spectrometric Studies of Gallium Arsenide Metalorganic Chemical Vapor Deposition: Trimethyl Gallium and Tertiary-Butyl Arsine on GaAs(100)

ABSTRACTLow pressure (∼10−5 Torr) studies of the adsorption and decomposition of tertiarybutyl arsine (t-BAs) on three different GaAs(100) surfaces (Ga-rich, H-atom treated and high temperature t-BAs treated) are presented. Mass spectrometric studies indicate that the primary gas-phase products of t-BAs decomposition on GaAs(100) are the tertiary-butyl radical and incomplete arsenic hydrides (predominantly AsH2). Infrared spectroscopic studies show that on H-atom treated and high-temperature t-BAs treated surfaces, t-BAs decomposes leaving behind very small quantities of alkyl groups. On Ga-rich surfaces however, significant amounts of alkyl products are observed. The surface species resulting from the adsorption of trimethyl gallium (TMG) are shown to be different at room temperature and high temperature.

Determination of Arsenic in Beer by Dry Ashing, Hydride Generation Atomic Absorption Spectroscopy

A method has been developed for determination of arsenic in beer. Organic matter is destroyed by the dry-ashing technique, the ash is dissolved in HCl, and hydrides of arsenic are generated by addition of sodium borohydride prior to atomization in a flame-heated quartz cell and atomic absorption spectroscopy measurement. The analytical features of the method are detection limit 0.1 ng/g beer, precision 8%, and recovery 97 +/- 7%. The arsenic contents of different brands from Spain and other European countries were analyzed. In all samples, the arsenic levels found were well below maximum levels allowed in Spanish legislation (100 ng/g). The quantities of arsenic in Spanish beers do not differ from those found in foreign beers. No differences were found between bottled and canned beers, and no correlation exists between metal content and original specific gravity of the beers.

Vibrational spectra of hydrogen atoms adsorbed on MBE-grown GaAs(100)

Internal reflection infrared spectroscopy was used for the first time to observe the vibrational spectrum of H atoms adsorbed on GaAs(100) surfaces grown by molecular beam epitaxy. Initial H atom exposure produces one peak at 2100 cm −1 due to an arsenic hydride species. With prolonged exposure, the 2100 cm −1 vibration disappears and a second one appears at 2140 cm −1 due to arsenic monohydride. Thus, for MBE-grown GaAs(100) only arsenic is accessible to the H atoms, and adsorption of H causes a change in the surface structure.

Utilization of Dual Phase Gas Diffusion FIA with a Mass Spectrometer as a Detector

Abstract The coupling of dual phase gas diffusion flow injection analysis with mass spectrometry has been shown to be feasible. This combined technique offers a high degree of selectivity and sensitivity. This technique was developed to determine whether volatile mixed arsenic selenium hydrides are formed in dual phase gas diffusion flow injection analysis hydride generation.

Thermal Diffusion in Metal‐Organic Chemical Vapor Deposition

The rate of chemical vapor deposition (CVD) can be significantly affected by thermal diffusion. Accurate predictions of growth rate and growth rate uniformity require accurate estimations of thermal diffusion factors. A complete first approximation of thermal diffusion factors, however, can be a complex process. We present a simple expression for estimating thermal diffusion factors for heavy molecules present in dilute concentrations in a light carrier gas, conditions that are usually valid for metal‐organic chemical vapor deposition (MOCVD). This simple expression yields approximations within a few percent of those calculated from a complete first approximation. The error for the methyl and ethyl organometallics of aluminum, gallium, and indium in hydrogen or helium is less than 1% at concentrations below 0.1% and less than 4% for concentrations below 0.5%. For hydrides of phosphorus, arsenic, or silicon in hydrogen or helium, the error is less than 3% at concentrations below 1%. Thermal diffusion factors for dilute concentrations of organometallics and hydrides in helium are greater than in hydrogen. Thermal diffusion factors are dependent on temperature, much more so for hydrogen carrier gas than for helium. Simple models are used to demonstrate the influence of thermal diffusion on MOCVD growth rate under both mass‐transfer controlled and kinetically controlled growth and on the composition of species incorporated under equilibrium‐controlled growth conditions.

Coupled chromatography-atomic spectrometry for arsenic speciation—a comparative study

Several methods for the quantitative determination of different forms of arsenic (AsIII, AsV, monomethyl and dimethyl) in a variety of samples are described and compared. In each instance separation is achieved by chromatographic means, using either gas (GC) or high-performance liquid chromatography (HPLC), with detection by atomic spectrometry, namely flame atomic absorption spectrometry (FAAS), flame atomic fluorescence spectrometry (FAFS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). For the GC separation it is necessary to derivatise the As compounds either as the hydrides or as the methylthioglycolates. As the arsenic hydrides can be pre-concentrated using cryogenic trapping, this yields the lowest detection limits. The As species studied can be separated without derivatisation by HPLC but after HPLC separation hydride generation can be used to increase the sensitivity for FAAS, FAFS and ICP-AES. While each technique is best suited to certain applications, the hydride generation-cryogenic trapping-GC-FAAS system is capable of detection at the sub-p.p.b. level (0.22–0.55 ng absolute for different species) and is preferred for low-level As samples. When levels permit, HPLC-hydride generation-FAAS is probably the simplest routine method and HPLC-hydride generation-ICP-AES will probably be preferred for multi-element analysis.

Arsenic speciation in water by hydride cold trapping-quartz furnace atomic absorption spectrometry: an evaluation

Arsenate, arsenite, monomethylarsonate, monoethylarsonate and dimethylarsinate are speciated in environmental waters. After pH-dependent hydride generation, the arsines are collected on a cold trap and volatilised sequentially into a quartz furnace atomic absorption spectrometer.The various parameters of the methodology are optimised, and their influence critically discussed and compared with other methods. Aspects such as interferences in organoarsenic speciation, the effect of atomisation support gases in collection mode techniques and unambiguous identification of dimethylarsine are emphasised in particular. An evaluation of the analytical characteristics and performance of the method is presented, using representative environmental samples. This paper attempts to illustrate the advantages and drawbacks of the technique and includes a review of recent progress in arsenic hydride methodology.

ChemInform Abstract: Synthesis of a Pentamethylcyclopentadienyl and Supermesityl‐Substituted Diphosphene and Phosphaarsene.

AbstractReaction of the dichlorophosphine or ‐arsine (I) with the phosphide (II) yields the compounds (III) which are dehydrohalogenated, forming the diphosphene or phosphaarsene (IV).

Simultaneous determination of arsenic, mercury, antimony and selenium in biological materials with prior collection of gaseous products followed by neutron activation analysis

A method combining prior collection of gaseous products with subsequent neutron activation analysis has been developed for simultaneous determination of traces of arsenic, mercury, antimony and selenium in biological materials. The generation of hydrides of arsenic, antimony and selenium and cold vapor of mercury in the vapor generaion and collection system was investigated by the use of radiotracers of the respective elements. The result indicates that selenium and mercury can be completely evaporated from the digested sample solution in 5M HCl with the addition of 5% sodium tetrahydroborate solution, while additional reduction proces by potassium iodide and ascorbic acid is needed for complete evaporation of arsenic and antimony. The gaseous products were collected in a quartz tube for neutron irradiation. The detection limits of these elements were fount to be in the range of 10−7 to 10−8 g under the present experimental conditions. The reliability was checked with NBS standard reference materials.