Showing papers on "Diborane published in 1999"

Activation of [Cp2ZrMe2] with new perfluoroaryl diboranes: Solution chemistry and ethylene polymerization behavior in the presence of MeAl(BHT)2

Abstract: Reversible C6F5transfer takes place between the boron centers in the anion formed by methide abstraction from [MeZr{N(SiMe3)2}3] or [Cp2ZrMe2] (LnM−CH3 in the reaction scheme) by the perfluorinated diborane 1. The solution chemistry of the metallocenium ion pairs formed from 1 and [Cp2ZrMe2] is correlated with the observed ethylene polymerization behavior of 1 in comparison to the monoborane B(C6F5)3, the related diborane 1,2-C6H4[B(C6F5)2]2, and the 9,10-diboraanthracene compound 9,10-(C6F5)2C12B2F8.

Selective surface functionalization of polyolefins by plasma treatment followed by chemical reduction

Abstract: Polymer surfaces can be finished with functional groups upon exposure to a plasma. Species of the plasma gas are attached at surface carbon atoms, forming functional groups of different composition. To produce a modified polymer surface with a high density and homogeneity of hydroxyl groups only, the oxygen-plasma-formed oxygen functional groups were chemically reduced by diborane and LiAlH4 with yields of 10 to 11 OH groups per 100 carbon atoms in the 3 to 5 nm near-surface layer as detected by X-ray photoelectron spectroscopy (XPS). The identification of hydroxyl groups was performed by means of attenuated total reflectance–Fourier transform infrared spectroscopy and XPS.

Diborane(4)yl Complexes of Molybdenum and Ruthenium

Abstract: Two new diborane(4)yl complexes [Br(Me2N)B−B(NMe2)M(C5H5)(CO)n] (M(C5H5)(CO)n = Ru(C5H5)(CO)2, Mo(C5H5)(CO)3) (1a, b) were obtained by the reaction of B2Br2(NMe2)2 with Na[M(C5H5)(CO)n]. These compounds were characterized in solution by IR and multinuclear NMR spectroscopy, and in the case of 1a by X-ray structure analysis, thus representing the first characterization of a ruthenium boryl complex in the crystal.

Unique Rearrangement of an Oxycarbyne Complex: Synthesis and Structure of Novel Diborane(4)yl Complexes.

Abstract: Nucleophilic attack of a carbonyl oxygen atom of the complexes K[(eta(5)-C(5)H(5))M(CO)(3)] (M=Mo, W) on each boron center gave the oxycarbyne complexes 1. These novel products undergo a unique type of rearrangement with quantitative formation of the diborane(4)yl complexes 2. Complex 2 (M=Mo) is the first structurally characterized boryl complex with a Mo-B bond (see structure).

The platinum catalysed diboration of alkynes using 1,2-b2cl2(nme2)2 : formation of 1-azonia-2-borata-5-borole derivatives

Abstract: The platinum catalysed diboration of alkynes using the diborane(4) compound 1,2-B2Cl2(NMe2)2 affords high yields of cyclic 1-azonia-2-borata-5-borole compounds, which arise from redistribution of B–Cl and B–NMe2 bonds.

Economical and convenient procedures for the synthesis of catecholborane

Abstract: New, economical and convenient procedures for the preparation of catecholborane in high chemically pure form using tri-O-phenylene bis borate readily prepared from the reaction of catechol with boric acid, and diborane or borane-Lewis base complexes.

In situ doping of silicon deposited by LPCVD: pressure influence on dopant incorporation mechanisms

Abstract: The influence of the silane pressure on the dopant incorporation during LPCVD silicon deposition at 550C using silane and phosphine or diborane (H) is examined, for a range of pressure from 1 to 100 Pa. We conclude that different deposition and dopant incorporation mechanisms occur according to the deposition pressure. It is shown that, under low-pressure conditions, silane remains the preponderant host species, while it is silylene at high pressure. At low pressure, and or H are separately but not independently adsorbed. At high pressure, the presence of silylene promotes the formation of monosilylphosphine and monosilylborane which are found to be the adsorbed dopant species. The usual change of the growth rate caused by the addition of the dopant, i.e. a reduction with phosphine and an increase with diborane, is a function of the silane pressure; the dopant content of the solid films causes a significant variation of the growth rate only when it is superior to a threshold of about in both cases.

Raman spectroscopic study on 100 facet of boron-doped chemical-vapour-deposited diamond crystals with fano line fitting

Abstract: We have investigated polarized Raman spectra on the {100} facet of B-doped CVD diamond single crystals grown under different diborane additions in the gas phase. An asymmetrical feature was observed on the one-phonon Raman line shape of B-doped diamond crystal which depended on the boron concentration. We have performed Fano line fitting for each one-phonon line of the Raman components. Fano parameters which were calculated from Fano line fitting quantitatively represented the asymmetry of the one-phonon line. The relation between Fano parameters and boron concentrations obtained in this study can predict a certain amount of boron concentration of B-doped diamond. The difference of the Fano asymmetric parameters q between that obtained from 〈100〉 and 〈110〉 decreased with increasing boron concentration. This tendency was similar to that observed in the relation between the crystallinity and boron concentration. We suggest that the asymmetry of the one-phonon line is dominantly induced by crystalline disorder with boron incorporation. Copyright © 1999 John Wiley & Sons, Ltd.

Gas-Phase Flash Reactions of Diborane, Triborane Carbonyl and Tetraborane with Alkynes

Abstract: Several known volatile closo -carboranes (1,5-C 2 B 3 H 5 , 1,6-C 2 B 4 H 6 , 2,4-C 2 B 5 H 7 , 1,10-C 2 B 8 H 10 ) and their alkyl derivatives and ten new alkyl derivatives of these carboranes were identified from the thermal gas-phase flash reactions of B 2 H 6 , B 3 H 7 CO and B 4 H 10 with ethyne, propyne and but-2-yne. In addition, nido -C 4 B 2 H 6 and its methyl derivatives were obtained from B 2 H 6 -alkyne flash reactions. All carboranes found in these high-energy reactions are the most thermally stable isomers of their class. The non-isolable borane {B 3 H 7 } is suggested as the initiator in all thermal flash reactions reported here.

Growth of Polycrystalline Diamond Films Including Diborane and Oxygen in the Source Gas

Abstract: Boron-doped polycrystalline diamond with both (100) and (111) facets were grown by microwave plasma chemical vapor deposition with and without oxygen (O 2 ) to study effects of O 2 on surface morphology, crystal quality, and boron-doping concentration of the films. It was found by Raman spectroscopy that the addition of O 2 improved the film quality as evidenced by the decrease of both the full width at half-maximum of the 1333 cm -1 diamond peak and the background level. By the addition of 0.10-0.25% O 2 , the boron concentrations in the diamond decreased to the same extent by two orders of magnitude for both (100) and (111) facets, indicating that the oxygen is playing a role in the gas phase in suppressing the involvement of diborane. It was also observed by scanning electron microscopy that the (100) facets of the diamond grown with O 2 appeared darker than the (111) facets, while the opposite is the case for the films grown without O 2 . This is because the secondary electron emission was suppressed by a higher concentration of terminating species on the (100) facets as compared to the (111) planes, indicating the added oxygen is also affecting the chemistry of the diamond surface.

Preparation and purification of diborane

Abstract: BF3, CO2 or both are removed from a mixture containing these gases with B2H6 by contacting the mixture with an inorganic hydroxide such as LiOH. B2H6 is synthesized by contacting BF3 with KBH4.

Crystalline TCNQ and TCNE adducts of the diborane(4) compounds B2(1,2-E2C6H4)2 (E = O or S)

Abstract: Crystal structures of 1∶1 adducts of diborane(4) compounds and the electron acceptors TCNQ and TCNE, namely B2(1,2-E2C6H4)2·TCNQ (E = O or S) and B2(1,2-E2C6H4)2·TCNE (E = O or S), have been found to show predominantly two-dimensional heteromolecular packing motifs with a variety of interlayer packings.

Boron-doped a-SiOx:H films prepared by photo-CVD technique

Abstract: The optoelectronic and structural properties of p-type a-SiOx:H films have been studied. The deposition parameters e.g. chamber pressure and diborane to silane ratio are optimized to get a film with dark conductivity (σd) 7.9×10−6 S cm−1 and photoconductivity 9.3×10−6 S cm−1 for an optical gap (E04) of 1.94 eV. The decrease of optical gap accompanied by the increase of conductivity is due to less oxygen incorporation in the film, which is substantiated by the decrease of the intensity of SiO absorption spectra. The properties are very much effected by the chamber pressure and diborane to silane ratio.

Preparation and purification of diborane

Abstract: BF3, CO2or both are removed from a mixture containing these gases with B2H6by contacting the mixture with an inorganic hydroxide such as LiOH B2H6is synthesized by contacting BF3with KBH4

Purification of diborane

Abstract: BF 3 , CO 2 or both are removed from a mixture containing these gases with B 2 H 6 by contacting the mixture with an inorganic hydroxide such as LiOH. B 2 H 6 is synthesized by contacting BF 3 with KBH 4 .

The complete basis set and gaussian ab initio computational investigation mono-, di- and tri-protonated borane and mono-, di-, tri-, and tetra-protonated diborane structures and energies

Abstract: High levels of computational study was performed with the target being to determine geometries and energies of multiprotonated borane and diborane. The enthalpies of protonation and molecular association reactions for these compounds were computed. Their stabilities and possibilities to be obtained experimentally were discussed.

Growth and Characterization of BxGa1−xN on 6H-SiC (0001) by Movpe

Abstract: Boron was incorporated into GaN in order to determine its limits of solubility, its ability of reducing the lattice constant mismatch with 6H-SiC, as well as its effects on the structural and optical properties of GaN epilayers. BxGa1−xN films were deposited on 6H-SiC (0001) substrates at 950 °C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. A single phase alloy with x=0.015 was successfully produced at a gas reactant B/Ga ratio of 0.005. Phase separation into pure GaN and BxGa1−xN alloy with x=0.30 was deposited for a B/Ga reactant ratio of 0.01. This is the highest B fraction of the wurtzite structure alloy ever reported. For B/Ga ratio ≥ 0.02, no BxGa1−xN was formed, and the solid solution contained two phases: wurtzite GaN and BN based on the results of Auger and x-ray diffraction. The band edge emission of BxGa1−xN varied from 3.451 eV for x=0 with FWHM of 39.2 meV to 3.465 eV for x=0.015 with FWHM of 35.1 meV. The narrower FWHM indicated that the quality of GaN epilayer was improved with small amount of boron incorporation.

Atomic layer doping of SiGe

Abstract: We demonstrate atomic layer processing for P and B doping and for SiGe:C epitaxy using LP(RT)CVD between room temperature and 400°C. In the case of P doping, the process is self-limiting. P doses below one monolayer were deposited by separating adsorption of PH 3 and deposition of SiGe. Below 400 °C the dominant process is dissociative adsorption of PH 3 with an activation energy of 0.3 eV. At higher temperatures, desorption of P decreases the incorporated P concentration. The P dose incorporated into SiGe may be controlled by the partial pressures of phosphine and hydrogen. For B atomic layer doping, we find no self-limitation of diborane adsorption. At low diborane partial pressures it is possible to prepare B peaks with a concentration below one monolayer. In this case the doping is dominated by the dissociative adsorption of diborane at Si and Ge surface sites. Using high partial pressures of diborane, several monolayers of B can be deposited. The diborane is adsorbed at B occupied surface sites. The SiGe:C atomic layer epitaxy was found to be controlled by the dissociative adsorption of methylsilane at temperatures below 400°C. At these temperatures the process is self-limiting. An effective activation energy of (0.36±0.4) eV was determined for the dissociative adsorption of methylsilane.

Mechanochemical Reactions in the Chemistry of Boranes

Abstract: Major concepts, experimental methods and applied aspects of mechanochemistry are reviewed in this paper. Mechanochemical reactions involved in the consideration include syntheses of diborane(6), borane adducts (L · BH 3 ) with organic nitrogen-containing Lewis bases, borazine, tetrahydroborates of transition metals M(BH 4 ) n where M=Ti(III), Zr(IV), Hf(IV), U(IV), formation of metal–carborane closo -cluster SnC 2 B 9 H 11 and some other cluster systems. The listed solid-phase reactions were performed under mechanical activation of the mixture of starting compounds in hermetic rotational and vibratory ball mills. The usage of solvents as a medium is excluded from mechanochemical syntheses of this kind. Volatile boron-containing compounds are isolated from the reaction medium by evaporation. Composition of initial mixtures, as well as conditions of mechanical activation, temperature regimes, and activation time affecting results of mechanochemical reactions under consideration are described and discussed in comparison with conventional synthesis methods.

The CVD of Ceramic Materials: Borides, Silicides, III–V Compounds and II–VI Compounds (Chalcogenides)

Abstract: This chapter reviews the basic properties, major chemical vapor deposition (CVD) reactions and processes, and the present and potential applications of the ceramic materials, particularly borides and silicides. Boron forms stable borides with the transition metals. The refractory-metal borides have a structure, which is dominated by the boron configuration. This favors the metallic properties such as high electrical and thermal conductivities and high hardness. Boriding by CVD is a simple process in which a layer of boron is deposited on a metal substrate, followed by heat treatment. The boron can also be deposited by the hydrogen reduction of chloride or by the decomposition of diborane. During heat treatment, the metal boride is formed by the solid-state diffusion of the boron atoms into the metal lattice to form an interstitial compound, while the direct boride deposition does not require a reaction with the substrate to form the boride. Some of its applications include: experimental TiB 2 coatings for cemented carbide cutting tools and other wear and erosion-resistant applications, and ZrB 2 coatings for solar absorption. The chapter discusses the CVD of III–V compounds and chalcogenides.

Ultrafine particles produced by plasma enhanced chemical vapor deposition -from SiH4, CH4, NH3 and B2H6 gas mixtures- for nanostructured ceramics aplications

Abstract: Ultrafine particles of silicon and related binary and ternary alloys of the Si-B-C-N system produced in our research group from silane, methane, diborane, ammonia and nitrogen precursor gases by plasma enhanced chemical vapor deposition at low pressure and room temperature are reviewed. The in-situ techniques of plasma analysis and surface characterization (quadrupolar mass spectrometry, optical emission spectroscopy and ellipsometry) providing evidence of powder formation and the polymerization reactions based on the SinH2n - negative radicals electrically confined in the plasma sheath are described. The square wave modulation (SQWM) of the rf power is discussed as an efficient method of controlling the powder particle production with low particle-size dispersion. The properties of the powder particles determined by different structural characterization techniques providing their size and distribution, crystalline order and morphology, chemical composition and chemical bond vibrational characteristics, are analyzed and discussed. Resum

Growth of Polycrystalline Diamond Films Including Diborane and Oxygen in the Source Gas.

Abstract: Boron-doped polycrystalline diamond with both (100) and (111) facets were grown by microwave plasma chemical vapor deposition with and without oxygen (O 2 ) to study effects of O 2 on surface morphology, crystal quality, and boron-doping concentration of the films. It was found by Raman spectroscopy that the addition of O 2 improved the film quality as evidenced by the decrease of both the full width at half-maximum of the 1333 cm -1 diamond peak and the background level. By the addition of 0.10-0.25% O 2 , the boron concentrations in the diamond decreased to the same extent by two orders of magnitude for both (100) and (111) facets, indicating that the oxygen is playing a role in the gas phase in suppressing the involvement of diborane. It was also observed by scanning electron microscopy that the (100) facets of the diamond grown with O 2 appeared darker than the (111) facets, while the opposite is the case for the films grown without O 2 . This is because the secondary electron emission was suppressed by a higher concentration of terminating species on the (100) facets as compared to the (111) planes, indicating the added oxygen is also affecting the chemistry of the diamond surface.