Showing papers on "Diborane published in 2003"

Semiconductor device and method of manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To enable an a-Si film to be precisely doped with impurities of low concentration. SOLUTION: An a-Si film 3 is formed on a glass substrate 1, while being loaded with impurities (boron), nickel 5 is added to the film 3, and the film 3 is turned to a crystalline silicon film 7 by a thermal treatment and irradiation with a laser beam 6. At this time, diborane gas which is diluted with hydrogen gas with a concentration 100 ppm is fed for 15 seconds, after the a-Si film 3 starts to be formed. By this setup, even if a comparatively high concentration of diborane gas which is stable in concentration and diluted to have a concentration of 100 ppm is fed, the average concentration of boron contained in the a-Si film 3 can be accurately set at a low value, such as about 1E12 atoms/cm or so. The boron concentration is set at 1E11 atoms/cm to 1E13 atoms/cm , by which the threshold voltage of a TFT can be controlled to an accuracy of the order of a few volts.

Energy decomposition analysis of the chemical bond in main group and transition metal compounds

Abstract: The nature of the chemical bond in the main group diborane(4) compounds X2B–BX2 (X = H,F,Cl,Br,I) and in the Fischer- and Schrock-type transition metal carbene and carbyne complexes and heavier homologues (CO)5W–CH2, (CO)5W–E(OH)2, Cl4W–EH2, Cl(CO)4W–EH and Cl3W–EH (E = C,Si,Ge,Sn,Pb) have been investigated with an energy decomposition analysis (EDA). The results give a deep insight into the nature of the chemical interactions. The EDA results can be used as a bridge between the heuristic models of experimental chemists which have been proven as useful ordering schemes for experimental observations and the physical mechanism which leads to a chemical bond. At the time the data give a well defined qantitative answer to the questions about the strength of the covalent and electrostatic interactions and about the contributions of σ and π electrons to the covalent bond.

The Infrared Spectrum of Al2H6 in Solid Hydrogen

Abstract: Although many volatile binary boron hydride compounds are known, binary aluminum hydride chemistry is limited to the polymeric (AlH3)(n) solid. The reaction of laser-ablated aluminum atoms and pure H2 during codeposition at 3.5 kelvin, followed by ultraviolet irradiation and annealing to 6.5 kelvin, allows dimerization of the intermediate AlH3 photolysis product to form Al2H6. The Al2H6 molecule is identified by seven new infrared absorptions that are accurately predicted by quantum chemical calculations for dibridged Al2H6, a molecule that is isostructural with diborane.

Infrared spectra of aluminum hydrides in solid hydrogen: Al2H4 and Al2H6.

Abstract: The reaction of laser-ablated Al atoms and normal-H2 during co-deposition at 3.5 K produces AlH, AlH2, and AlH3 based on infrared spectra and the results of isotopic substitution (D2, H2 + D2 mixtures, HD). Four new bands are assigned to Al2H4 from annealing, photochemistry, and agreement with frequencies calculated using density functional theory. Ultraviolet photolysis markedly increases the yield of AlH3 and seven new absorptions for Al2H6 in the infrared spectrum of the solid hydrogen sample. These frequencies include terminal Al−H2 and bridge Al−H−Al stretching and AlH2 bending modes, which are accurately predicted by quantum chemical calculations for dibridged Al2H6, a molecule isostructural with diborane. Annealing these samples to remove the H2 matrix decreases the sharp AlH3 and Al2H6 absorptions and forms broad 1720 ± 20 and 720 ± 20 cm-1 bands, which are due to solid (AlH3)n. Complementary experiments with thermal Al atoms and para-H2 at 2.4 K give similar spectra and most product frequencies w...

Isobutene polymerization using a chelating diborane co-initiator.

Abstract: Lewis acidic diborane 1 (J. Am. Chem. Soc. 1999, 121, 3244−3245) is highly effective for both proton- and cationogen-initiated isobutene polymerization in hydrocarbon media at low temperature. Reactions of diborane 1 with cumyl chloride and cumyl methyl ether were studied by variable-temperature 1H and 19F NMR spectroscopy. At low temperatures stable ion pairs 2a and 2b are formed; at higher temperatures these ion-pairs form phenyl-1,3,3-trimethylindan (3) with concomitant release of HCl to form 1 in the case of 2a or degradation of the anion (2b). Reaction between Ph3C−Cl and diborane 1 resulted in the generation of an ion-pair 4 consisting of the Ph3C cation very weakly associated with the chelated, μ-Cl counteranion as revealed by X-ray crystallography.

Evolving patterns in boron cluster chemistry

Abstract: This paper outlines the development of our knowledge and understanding of the structures and bonding of boron cluster compounds, with particular reference to the evolving complementary roles localized bonding and molecular orbital treatments have played in providing simple rationalizations of their polyhedral molecules. INTRODUCTION: EARLY DEVEL OPMENTS The polyhedral patterns that characterize boron cluster chemistry have provided rich pickings for the structural and bonding enthusiast since they first become apparent, too rich to do justice to in a short paper. Here, we outline how those patterns and our attempts to understand them have evolved. Life itself, at least as we know it, evolved in an electron-rich world, one in which there was such an abundance of electrons that our early ideas about valency assumed that at least two electrons, shared between a pair of atoms, were needed to form a covalent chemical bond between them (1). Early boranes provided a challenge to this by existing despite their apparent electron deficiency. Compounds B n H n+4 (n = 2, 5, 6, or 10) and B n H n+6 (n = 4 or 5), prepared in A. Stock's pioneering researches (2), in which he invented vacuum line technology to deal with these highly reactive substances, were labeled "electron-deficient" because they contained too few electrons to provide a pair for every 2-center link in their molecules, evident even before their molecular structures were determined. Containing (2n + 4) or (2n + 6) atoms respectively these borane molecules have only (2n + 2) or (2n + 3) valence shell electron pairs, fewer than the minimum number, (2n + 3) or (2n + 5), of 2-center links required. A real structural breakthrough was provided by R. P. Bell and H. C. Longuet-Higgins. They deduced the structure of diborane, B 2 H 6 , from its vibrational spectrum (3). The value of the 3c2e bond concept, to explain its BHB links, soon followed. Subsequently, W. N. Lipscomb put borane structural chemistry on a sound basis by his classic low-temperature X-ray crystallographic studies of key boranes B n H n+m and perceptive analysis of the bonding implications of their intricate structures (4). He noted that the n boron atoms and m (endo) hydrogen atoms lay on an inner, near-spherical surface; the remaining n (exo) hydrogen atoms lay on an outer sphere, attached to the boron atoms by 2c2e BH bonds pointing radially outwards from the cluster center. Bonding between the boron and endo-hydrogen atoms on the inner sphere involved (2n + m) electrons (two from each BH unit, one from each endo-hydrogen) which Lipscomb allocated to four types of localized electron pair bonds, s BHB and t BBB 3c2e bonds and y BB and x BH 2c2e bonds. Electron, orbital, and boron atom counts led to three equations linking the values of s, t, y, and x to n and m: s = m - x = n - t = 2y + x

On the spectroscopic detection of neutral species in a low-pressure plasma containing boron and hydrogen

Abstract: Spectroscopic studies of microwave discharges in H2–Ar–B2H6 gas mixtures (f = 2.45 GHz, P = 1.2–3.5 kW, p = 1–8 mbar) have been performed to improve the possibilities of diagnostics of non-equilibrium, low-pressure plasmas containing boron and hydrogen. For this purpose, UV–VIS optical emission spectroscopy and infrared absorption spectroscopy with tunable diode lasers (TDLAS) have been applied. It is shown that information about neutral species and the gas temperature may be obtained by means of new and modified spectroscopic methods. A method for the determination of the absolute number density of boron atoms from measured relative intensities of the components of the boron resonance doublet (distorted by reabsorption) is proposed and tested for validity. The maximum of the density was found to be 3.8 × 10 11 atoms cm −3 at an admixture of diborane of about 2%. The gas temperature was determined from the intensity distributions in the rotational structure of the emission bands of BH and H2 and from Doppler broadening of the absorption line profiles of the BH molecule. It was observed that values of the gas temperature obtained from the rotational intensity distributions are in good agreement with those obtained from Doppler widths (Tg = 700–1070 K). Based on measurements of the relative line intensities of atomic and molecular hydrogen and the gas temperature, and using a simple excitation–deactivation model, the density of molecular hydrogen was found to be about 40 times higher than the density of atomic hydrogen. It is shown that some absorption lines of boron hydrides (B2H6, BH3 and BH) detected by TDLAS may be used for plasma diagnostics.

Selective Hydroboration of a 1,3,7‐Triene: Homogeraniol

Abstract: Selective hydroboration of a 1,3,7-triene: homogeraniol intermediate: geranial solvent: 200 mL of petroleum ether intermediate: 13.0 g (86.7 mmol) of (E)-4,8-dimethyl-1,3,7-nonatriene product: homogeraniol intermediate: 1–2% of the Z isomer. Keywords: addition, to CC; addition, to CO; condensation, carbonyl-ylide condensation; hydroboration; oxidation, CHOH CO; assay methods, for diborane solutions; dichloromethane (methylene chloride); dimethyl sulfoxide; 2-methyl-2-butene; methyltriphenylphosphonium iodide; tetrahydrofuran

Amorphous boron nanoparticles and BN encapsulating boron nano-peanuts prepared by arc-decomposing diborane and nitriding

Abstract: Amorphous boron nanoparticles were prepared by arc-decomposing diborane, which had ideal morphologies in comparison with that of those fabricated by furnace or laser heating diborane. Peanut-shaped boron nitride encapsulating boron nanocapsules were fabricated by nitridation of amorphous boron nanoparticles. Unique core/void/shell structure of the nanocapsules was observed by using a high-resolution transmission electron microscopy. The mechanism of growing the BN nanocapsules by a catalyst free process was distinctly different from the process of arc discharge or laser heating. The broadening of nonpolar intralayer Raman line of hexagonal BN at about 1370 cm−1 was observed, which was attributed to the small crystal size of BN.

Surface segregation of boron in BxGa1−xAs/GaAs epilayers studied by x-ray photoelectron spectroscopy and atomic force microscopy

Abstract: The behavior of boron incorporation into GaAs has been studied by x-ray photoelectron spectroscopy, x-ray diffraction, and atomic force microscopy. As the boron content of the film was increased, both the characteristic peak for the B 1s core level at 188 eV and As Auger transition (260 eV) could be detected by XPS. At 550–600 °C, single crystalline films could only be grown for x⩽0.06. Upon increasing the diborane flux in the gas phase, the film stoichiometry and the boron surface composition evolved rapidly towards a boron-rich subarsenide compound. This trend is followed by a clear degradation of the surface morphology and an increase in the surface roughness. A surface segregation of boron is suggested due to the high diborane vapor supersaturation needed during growth.

Effects of Boronization in LHD

Abstract: Boronization (boron coating) using diborane was carried out in the Large Helical Device (LHD) for wall conditioning. Using three nozzles for the diborane supply, about 60 % area of the vacuum chamber was covered by boron film. Oxygen impurity radiation was strongly reduced by gettering, and radiation from carbon and metals were reduced about 30 – 40 % by coverage with boron film. As a result, radiation loss was reduced and the operational density exceeded 1·10 20 cm –3 , which is about twice of that before boronization.

Chapter 4 Boron doping of diamond films from the gas phase

Abstract: Publisher Summary This chapter discusses the boron doping of diamond films from the gas phase. The goal of boron incorporation is p-type doping of the diamond films. However, it has also important effects on the physicochemical properties of these films. The effect of their boron content is reviewed on some physicochemical and electrical properties of homoepitaxial, highly oriented, and polycrystalline boron diamond films. The boron incorporation from the gas phase to the solid phase depends on the deposition technique and on the deposition conditions, on the monocrystalline or polycrystalline nature of the films. Undoped homoepitaxial diamond films contain impurities and defects. Their concentrations are still higher in highly oriented and polycrystalline films, which contain additionally amorphous and graphitic parasitic phases. Numerous precursors have been used to incorporate boron in the films, but more currently diborane and trimethylboron are used. The incorporation from the gas to the solid phase is not completely understood, but is efficient.

Effect of nitrogen addition on the morphology and structure of boron-doped nanostructured diamond films

Abstract: A chemical vapor deposition hydrogen/methane/nitrogen feedgas mixture with unconventional high methane (15% CH4 by volume) normally used to grow ultrahard and smooth nanostructured diamond films on Ti–6Al–4V alloy substrates was modified to include diborane (10% B2H6 in hydrogen) for boron doping. The flow rates of N2 were varied to investigate its effect on plasma chemistry, film morphology, and mechanical properties. As expected, boron is readily incorporated into the diamond film and results in a change in the lattice parameter. Nitrogen, on the other hand, competes with boron in the plasma and acts to prevent boron incorporation into the diamond structure. Glancing angle x-ray diffraction indicates a decrease of diamond lattice parameter with increasing N2/CH4 flow rate ratio. A critical N2/CH4 ratio of 0.4 was found to result in a film with a minimum in grain size and surface roughness, along with high boron incorporation (∼4×1020 cm−3). As shown from this critical limit, experimental conditions can ...

Gas Phase Reactions between SiH4 and B2H6: A Theoretical Study

Abstract: Gas-phase reactions of silane (SiH4) and diborane (B2H6) are investigated using ab initio calculations at the MP2/6-311++g** level. Initially SiH4 and B2H6 are only weakly attracted to each other. Under thermal activation, the two molecules can overcome an energy barrier of 33.87 kcal/mol to associate into a complex SiH4−BH3−BH3 with a hydrogen-bridged Si−H−B bond. Upon bonding, one of the two hydrogen-bridged bonds B−H−B in B2H6 is broken and the other becomes polarized. Started from the SiH4−BH3−BH3 complex, three comparable fragmentation pathways involving BH3 and H2 elimination produce several silaboranes with various silicon−boron−hydrogen ratios. A much higher barrier exists between the initial loosely bonded SiH4−B2H6 system and a direct H2 elimination product SiH3−B2H5 with Cs symmetry. The bonding nature in the species are further elucidated through topological analysis of electron density using the AIM theory. These intermediate silaboranes are possible precursors for chemical vapor deposition i...

A high-level calculation of the proton affinity of diborane

Abstract: The experimental proton affinity of diborane (B 2 H 6 ) is based on an unstable species, B 2 H 7 + , which has been observed only at low temperatures. The present work calculates the proton affinity of diborane using the Gaussian-3 method and other high-level compound ab initio methods as a check of the experimental value. The present value of the proton affinity of diborane is thus reported at 147.7 kcal/mol, compared with the experimental value of 147±4 kcal/mol. However, the experimental value was found to be based on two values, each of which are presently held in error by 12 kcal/mol, but in opposite directions.

Oxide, Sulfide, Selenide, and Borane Derivatives of Indenylphosphines

Abstract: We report the preparation, isolation and characterization of oxide, sulfide, selenide, and borane derivatives of a series of indenylphosphines Some members of the series had already been prepared, and we have completed the series We have prepared (indenyl)xPh3-xPO (x = 1–3) for the oxide series, (indenyl)xPh3-xPS (x = 3) for the sulfides, (indenyl)xPh3-xPSe (x = 1,2) for the selenides, and (indenyl)xPh3-xPBH3 (x = 1–3) for the boranes Linear relationships of the 31P NMR chemical shift with the number of indenyl groups were observed The compounds were also characterized by 1H and 13C NMR spectroscopy and mass spectrometry The solid-state structure of diindenylphenylphosphine selenide was determined by X-ray crystallography and found to be isomorphous with diindenylphenylphosphine sulfide The solid-state structure of triindenylphosphine sulfide was also determined by X-ray crystallography and the indenyl groups were confirmed to all be the inden-3-yl isomer Additionally, pentacarbonyl(triindenylphosphine)molybdenum(0), 1,3-bis(diphenylphosphino)indene diborane, and rac-bis(1-(diphenylphosphino)indenyl)ironII) diborane were prepared, isolated, and characterized

Mechanical Properties of Boron Doped Diamond Films Prepared by MPCVD

Abstract: A chemical vapor deposition hydrogen/methane/nitrogen feedgas mixture with unconventionally high methane (15% CH4 by volume) normally used to grow ultra-hard and smooth nanostructured diamond films on Ti-6Al-4V alloy substrates was modified to include diborane (10% B2H6 in hydrogen) for boron-doping. The flow rate for B2H6 was varied to investigate its effect on plasma chemistry, film structure, and mechanical properties. It was found that boron in the plasma can easily be incorporated into diamond films and change the lattice parameter and affect film structure as measured by Raman spectroscopy. Grazing angle x-ray diffraction shows a strong dependence of diamond lattice parameter with diborane flow rate and B2H6:CH4 flow rate ratio. Thermal stability of these films was evaluated by heating in an oxygen environment above 700 °C. Nanoindentation measurements show that the films have high hardness close to that of nanostructured diamond. High film hardness and toughness, combined with good thermal stability and low surface roughness indicate great potential as wear resistant coatings able to withstand high temperature oxidizing environments.

Molecular dynamics and quantum chemical studies on diborane

Abstract: Within the limitations of AM1 (restricted Hartree–Fock) type semiempirical quantum chemical calculations, molecular dynamics of B2H6 system at constant temperature conditions was investigated. Adopting the molecular geometry at an elevated temperature certain molecular orbital characteristics of B2H6 were obtained. Also, the vibrational spectrum at the elevated temperature was compared with the corresponding one at T=0 K .

Chemical synthesis and characterization of boron/boron nitride core–shell nanostructures

Abstract: A moderate chemical method [i.e., the reaction of diborane (B2H6) and a mixture gas of ammonia and nitrogen (NH3/N2) over nanoscale iron boride at 1100 °C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core–shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.

Infrared Spectra of Aluminum Hydrides in Solid Hydrogen: Al2H4 and Al2H6.

Abstract: The reaction of laser-ablated Al atoms and normal-H2 during co-deposition at 3.5 K produces AlH, AlH2, and AlH3 based on infrared spectra and the results of isotopic substitution (D2, H2 + D2 mixtures, HD). Four new bands are assigned to Al2H4 from annealing, photochemistry, and agreement with frequencies calculated using density functional theory. Ultraviolet photolysis markedly increases the yield of AlH3 and seven new absorptions for Al2H6 in the infrared spectrum of the solid hydrogen sample. These frequencies include terminal Al−H2 and bridge Al−H−Al stretching and AlH2 bending modes, which are accurately predicted by quantum chemical calculations for dibridged Al2H6, a molecule isostructural with diborane. Annealing these samples to remove the H2 matrix decreases the sharp AlH3 and Al2H6 absorptions and forms broad 1720 ± 20 and 720 ± 20 cm-1 bands, which are due to solid (AlH3)n. Complementary experiments with thermal Al atoms and para-H2 at 2.4 K give similar spectra and most product frequencies w...

Gas-Phase Reactions between Diborane and Carbon Monoxide: A Theoretical Study

Abstract: Experimentally, gas-phase reactions between diborane (B2H6) and carbon monoxide (CO) produce borane carbonyl (BH3CO) and a less volatile material. To elucidate the unknown part of the products, we ...

Gas Phase Reactions Between SiH4 and B2H6: A Theoretical Study.

Abstract: Gas-phase reactions of silane (SiH4) and diborane (B2H6) are investigated using ab initio calculations at the MP2/6-311++g** level. Initially SiH4 and B2H6 are only weakly attracted to each other. Under thermal activation, the two molecules can overcome an energy barrier of 33.87 kcal/mol to associate into a complex SiH4−BH3−BH3 with a hydrogen-bridged Si−H−B bond. Upon bonding, one of the two hydrogen-bridged bonds B−H−B in B2H6 is broken and the other becomes polarized. Started from the SiH4−BH3−BH3 complex, three comparable fragmentation pathways involving BH3 and H2 elimination produce several silaboranes with various silicon−boron−hydrogen ratios. A much higher barrier exists between the initial loosely bonded SiH4−B2H6 system and a direct H2 elimination product SiH3−B2H5 with Cs symmetry. The bonding nature in the species are further elucidated through topological analysis of electron density using the AIM theory. These intermediate silaboranes are possible precursors for chemical vapor deposition i...

Low Resistivity Boron Doped Amorphous Silicon-Germanium Alloy Films Obtained with a Low Frequency

Abstract: The structural and electrical properties of boron doped amorphous silicon-germanium alloy films, obtained using a low frequency plasma enhanced chemical vapor deposition (LF PECVD), are presented in this contribution. These thin films were deposited on a substrate heated at 270°C, and by decomposing a mixture of silane, germane, and diborane gases. The chemical bond structure was studied by Infrared Spectroscopy. Our results show that, for a constant diborane flow, the increase of germane flow enhances the incorporation of boron into the film; the peak at 2540 cm−1 becomes larger as the Ge content increases. Transport of carriers was studied by measuring current-voltage curves as a function of temperature. The conductivity increased from 10−6 to 10 (Q-cm)−1, while the refraction index increased from 3.312 to 4.4458, for an increasing Ge content; this makes the films suitable for optical waveguide applications. On the other hand, the activation energy varied from 0.668 to 0.220 eV when the sample was doped with boron. The AFM images showed that the surface roughness was improved for an alloy with 50% of Ge.

The Infrared Spectrum of Al2H6 in Solid Hydrogen.

Abstract: Although many volatile binary boron hydride compounds are known, binary aluminum hydride chemistry is limited to the polymeric (AlH3)(n) solid. The reaction of laser-ablated aluminum atoms and pure H2 during codeposition at 3.5 kelvin, followed by ultraviolet irradiation and annealing to 6.5 kelvin, allows dimerization of the intermediate AlH3 photolysis product to form Al2H6. The Al2H6 molecule is identified by seven new infrared absorptions that are accurately predicted by quantum chemical calculations for dibridged Al2H6, a molecule that is isostructural with diborane.