Showing papers on "Diborane published in 1986"

Doping reaction of PH3 and B2H6 with Si(100)

Abstract: The reaction of phosphine PH3 and diborane B2H6 on Si(100) surfaces was studied by surface analytical techniques in relation to the in situ doping process in the chemical vapor deposition of silicon. Phosphine chemisorbs readily either nondissociatively at room temperature or dissociatively with the formation of silicon–hydrogen bonds at higher temperatures. Hydrogen can be desorbed at temperatures above 400 °C to generate a phosphorus layer. Phosphorus is not effective in shifting the Fermi level until the coverage reaches 2×1014/cm2. A maximum shift of 0.45 eV toward the conduction band was observed. In contrast, diborane has a very small sticking coefficient and the way to deposit boron is to decompose diborane directly on the silicon surface at temperatures above 600 °C. Boron at coverages less than 2×1014/cm2 is very effective in shifting the Fermi level toward the valence band and a maximum change of 0.4 eV was observed.

Selective reductions. 38. Reaction of thexylchloroborane-methyl sulfide complex in methylene chloride with selected organic compounds containing representative functional groups. Comparison of the reducing characteristics of thexylchloroborane, thexylborane, and diborane

Abstract: On definit les caracteristiques du reactif pour des reductions selectives. Comparaison de ces caracteristiques avec celles du thexylborane et du diborane

Doped hydrogenated amorphous silicon films by laser‐induced chemical vapor deposition

Abstract: We report the growth and characterization of both n‐type and p‐type doped hydrogenated amorphous silicon films prepared by laser‐induced chemical vapor deposition. For both doping types, the activation energy for electrical conduction has been reduced to below 0.2 eV and controlled doping has been achieved. Phosphine lowers the growth rate, while diborane has essentially no effect on the laser‐induced growth but enhances thermal growth. Diborane also decreases the hydrogen concentration of the films, resulting in reduced optical gaps.

Selective Reduction of Imines with the Diborane-Methanol System

Abstract: The selective reduction of imines with the diborane-methanol system was investigated. This system reduced imines quantitatively, and other functional groups tested were unaffected.

Modification of H-mordenite with silane and diborane. A comparative study of the reaction parameters

Abstract: Silane and diborane have been found to be very suitable for the structural modification of H-mordenite. The reaction with silane or diborane reduces, in a controlled way, the effective pore size of zeolites by implantation of additional atoms or atom groups. As a result, molecular sieving effects can be controlled by pore size engineering, and gases can be encapsulated under moderate conditions of temperatures and pressures by closing the zeolitic pores by silanation or boranation techniques.The main parameter determining the efficiency of a pore closure, is the degree of modification: the amount of silane or diborane chemisorbed in the zeolite. The effect of reaction temperature, reaction pressure and reaction time on the degree of modification is studied for silanation and boranation of H-mordenite.Generally, for silanation and boranation it was observed that the modification degree increases with increasing pressure of the modifying agent. For silanation we observed that a higher reaction temperature enhances primary and secondary reactions. Increasing the pressure of silane decreases the ratio secondary/primary reactions, while the chemisorption of silane by primary reaction is favoured at higher pressure. Compared to the silanation, the boranation reaction is very fast because of the higher reactivity of diborane towards zeolitic hydroxy groups. Even at room temperature and low pressure the ultimate boranation degree could be reached. For the boranation we observed an indirect pressure effect which has an important influence on the ultimate modification and hence on the resulting porosity of the zeolite. The amount of added diborane, and hence the number of boranation steps, used to reach the ultimate boranation degree is a critical parameter in determining the pore size reduction.

Enantiomerically Pure Compounds via Chiral Organoboranes

Abstract: The ether catalyzed addition of diborane to unsaturated organic molecules -the hydroboration reaction — made organoboranes readily available for the first time. [1,2] Systematic study of these organoboranes has revealed that they are among the most versatile intermediates available to the organic chemist. [3] Indeed, it is possible to utilize organoboranes to synthesize essentially all structural types of organic compounds (Chart 1).

Properties of compensated and doped amorphous SiC and GeSi alloy films

Abstract: Hydrogen and fluorine incorporation in sputtered amorphous Si x Ge 1 − x and SiC films is described. Infrared and Raman spectroscopy is used to ascertain the amorphous nature of the films and to determine the amount of H and F incorporated and their nature of bonding. Incorporation of hydrogen or fluorine in the films is seen to increase with increasing partial pressure of hydrogen or fluorine. The identification of the different complexes present in the structure of these films and the assignment of different stretching, bending and/or wagging vibrational modes are discussed. Quantitative analysis of these spectra also reveal the relative preference of attachment by H or F to Ge, Si and C. Hydrogen and fluorine attach preferentially to Si and C for Si-Ge and SiC alloys respectively. H or F incorporated (− 40%) is much larger than the expected number of dangling bonds. However the number of states in the band gap steadily decreases with increasing H or F. Incorporation of H or F systematically increases the optical band gap and decreases the electrical conductivity. Hydrogen compensated SiC films are doped p or n types by incorporation of diborane or phosphine during sputtering. The atomic percentage of phosphorus and boron in the samples increases with increasing partial pressure of phosphine and diborane during deposition. The conductivity and thermoelectric power measurements are presented. These results show that doping has been achieved.

Method for detecting gaseous hydrides

Abstract: A solid detecting reagent for gaseous hydrides and a gaseous hydride detecting method are disclosed, said reagent comprising a basic copper carbonate as a color changing component and undergoing color change upon contact with at least one gaseous hydride selected from the group consisting of arsine, phosphine, diborane, hydrogen selenide, germane, monosilane, disilane and dichlorosilane. The reagent is applicable to all of these gaseous hydrides and, upon contact therewith, rapidly changes from an initial blue color to a black color, said black color standing for a long period of time.

Processes for producing silicon carbide particles and sinter

Abstract: Silicon carbide particles containing boron are produced by first reacting silicon or a silicon compound containing no carbon with boron or a boron compound containing no carbon in a first reaction zone at a temperature above the melting point of silicon and then reacting the boron-containing fused silicon particles so produced with a carbon compound in a second reaction zone at a temperature below the boiling-point of silicon. The silicon compound may be silane and the boron compound may be diborane, and they may be mixed before being introduced into the reaction zone.

Evaluation of the oxygen and hydrogen content in powdered boron and some of its compounds

Abstract: For a quantitative evaluation of the connection between the composition and the property of boron powder, the authors worked a method of determining the content of gas-forming components based on the reducing melting of material in graphite capsules in a stream of inert gas at 1400 K or more. The method was used for evaluating the content of oxygen and hydrogen in boron powders obtained by the method of pyrolysis of diborane.

The Implantation of Boron-Nitrogen Compounds in Mordenite LP and their Influence on the Adsorption Properties

Abstract: The structural modification of zeolites by chemisorption of diborane followed by reactions with amines (NH3, CH3NH2, C2H5NH2, (CH3)2NH) has been proven to be an important method to change in a controlled way the porosity creating new selectivities for different gases. The ultimate porosity of modified mordenite LP substrates was evaluated by the adsorption kinetics of Ar, Kr and Xe. The pore size of the mordenite LP can be changed gradually by variation of the amount of B2H6 chemisorbed, the nature of the amine and other parameters such as the reaction time and temperature. The boron-nitrogen (BN) compounds, formed inside the mordenite, were studied with photoacoustic FTIR-spectroscopy (PAS). These spectra show that at low temperatures amine-boranes are formed; at higher temperatures H2 is evolved and BN-polymers such as amino-boranes or boron-nitrid-like species are trapped inside the channels of the zeolite.

4-aminocotinine and production thereof

Abstract: NEW MATERIAL:4-Aminocotinine shown by the formula I USE:White crystal, compound having 125-126 degC melting point, and specific rotary power [alpha] d=-952 deg (c=07, MeOH), useful as an improved artificial antigen for nicotine, having pyridine ring, pyrrolidine ring, and optical activity important as an artificial antigen for nicotine PREPARATION:Cotinine shown by the formula II is oxidized with a preacid such as H2O2, etc to form cotinine-N-oxide shown by the formula III, which is reacted with conc sulfuric acid and fuming sulfuric acid to give 4- nitrocotinine-N-oxide shown by the formula IV This compound is reduced with iron in acetic acid to give 4-aminocotinine shown by the formula V, which is reduced with diborane to give easily the compound shown by the formula I

Photoelectronic and optical properties of B doped DC sputtered hydrogenated silicon nitride compounds

Abstract: We report on the optical and electronic properties of boron doped DC sputtered a-SixN1 − x: H films prepared in a wide range of dopant, hydrogen and nitrogen concentrations. It is shown that we can prepare intrinsic and photoconductive p-type films by varying the partial pressure of diborane in an Ar + N2 + H2 + B2H6 gas mixture whose total pressure is P1. Light doping of wide gap material (Eg ~ 2.25 eV) prepared in the following conditions Pt = 25 mT, PH2/Pt = 0.1, PN2/Pt = 0.013, 0 ≤ r = PB2H6/Pt ≤ 8 × 10−4 was first studied. For r up to 2 × 10−5, it is seen that boron doping produces a decrease in dark conductivity σd and an increase of activation energy Ea towards the intrinsic value Eg/2. Higher diborane pressures (2 × 10−5 A series of p-doped films was then grown using the following conditions: PAr = 25, 30, 35 mT, PB2H6 = 0.02 mT, PH2 varying from 0.5 to 2 mT and PN2 from 0.125 to 0.35 mT. Systematic study of σd, Ea, ημτ, σph(AM-1), Eg has been performed. For every film two dark conduction regimes are observed:extended-state conduction at high temperatures and hopping conduction in the valence band tail at low temperatures. From the change in activation energy of σd and the activation energy of ημτ, the valence band tail width EB - EV and the hopping energy W are deduced. As far as an application such as the window side junction of a p.i.n solar cell is concerned the best results correspond to PAr = 25 mT, PH2 = 1.75 mT, PN2 = 0.125 mT. One then has Eg ~ 1.85 eV, Ea ~ 0.5 eV, σd ~ σph(AM-1) ~ 10−7 (Ω cm)−1, ημτ ~ 10−7 cm2 V−1. Finally IR spectroscopy reveals that the integrated absorption coefficient over the 840 cm−1 Si-N band, I, first increases linearly with N content giving an oscillator strength factor of 7.5 × 1018 cm−2 and then becomes saturated whereas the N-H bands begin to grow. Furthermore it is shown that I is systematically lower for B-doped films than for undoped ones and that the B-N band grows with PB2H6. These results on B-doped films confirm that in addition to threefold bonded boron leading to a relaxation of the Si matrix, boron is largely incorporated at silicon sites surrounded with four silicon atoms and also at the other sites where B-N bonds are created.

Modification of H-Mordenite with Silane and Diborane. A Comparative Study of the Reaction Parameters.

Abstract: Silane and diborane have been found to be very suitable for the structural modification of H-mordenite. The reaction with silane or diborane reduces, in a controlled way, the effective pore size of zeolites by implantation of additional atoms or atom groups. As a result, molecular sieving effects can be controlled by pore size engineering, and gases can be encapsulated under moderate conditions of temperatures and pressures by closing the zeolitic pores by silanation or boranation techniques.The main parameter determining the efficiency of a pore closure, is the degree of modification: the amount of silane or diborane chemisorbed in the zeolite. The effect of reaction temperature, reaction pressure and reaction time on the degree of modification is studied for silanation and boranation of H-mordenite.Generally, for silanation and boranation it was observed that the modification degree increases with increasing pressure of the modifying agent. For silanation we observed that a higher reaction temperature enhances primary and secondary reactions. Increasing the pressure of silane decreases the ratio secondary/primary reactions, while the chemisorption of silane by primary reaction is favoured at higher pressure. Compared to the silanation, the boranation reaction is very fast because of the higher reactivity of diborane towards zeolitic hydroxy groups. Even at room temperature and low pressure the ultimate boranation degree could be reached. For the boranation we observed an indirect pressure effect which has an important influence on the ultimate modification and hence on the resulting porosity of the zeolite. The amount of added diborane, and hence the number of boranation steps, used to reach the ultimate boranation degree is a critical parameter in determining the pore size reduction.

Method for determining the presence of diborane in air

Abstract: Diborane is detected in air with high sensitivity (ppb range) and selectivity. The invention is thus suitable for the monitoring of work places and rooms, the emission of plants, etc. The detection is based on an aerosol ionization gas analysis. In addition to an amine, a reagent which does not react with amine is added to the air stream and reacts with the diborane to form a compound which forms aerosols with the amine. The aerosols obtained by this reaction constitute the main measuring effect. When using SO 2 in concentration≧3.5 ppm, disturbances due to the SO 2 content of the air are eliminated.