Showing papers on "Diborane published in 2000"

Optical second harmonic spectroscopy of boron-reconstructed Si(001)

Abstract: Optical second harmonic generation (SHG) spectroscopy is used to probe Si(001) following thermal decomposition of diborane at the surface. Incorporation of boron (B) at second layer substitutional sites at H-free Si(001) intensifies and redshifts the E1 SHG spectral peak, while subsequent H termination further intensifies and blueshifts E1, in sharp contrast to the effect of bulk B doping or nonsubstitutional B. Ab initio pseudopotential and semiempirical tight binding calculations independently reproduce these unique trends, and attribute them to the surface electric field associated with charge transfer to electrically active B acceptors, and rehybridization of atomic bonds.

MOCVD Growth of GaBN on 6H-SiC (0001) Substrates

Abstract: BxGa1−xN films were deposited on 6H-SiC (0001) substrates at 1000°C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. The presence of boron was detected by Auger scanning microprobe, the shift of the (00.2) x-ray diffraction peak, and low-temperature photoluminescence. A single-phase BxGa1−xN alloy with x=1.5% was produced at the gas phase B/Ga ratio of 0.005. Phase separation into wurtzite BGaN and the B-rich phase occurred for a B/Ga ratio in the 0.01–0.2 range. Only BN was formed for B/Ga >0.2. The B-rich phase was identified as h-BN with sp2 bonding based on the results of Fourier transform infrared spectroscopy. As the diborane flow exceeds the threshold concentration, the growth rate of BGaN decreases sharply, because the growth of GaN is poisoned by the formation of the slow growing BN phase. The bandedge emission of BxGa1−xN varies from 3.451 eV for x=0% with FWHM of 39.2 meV to 3.465 eV for x=1.5% with FWHM of 35.1 meV. The narrower FWHM indicates that the quality of GaN epilayer is improved with a small amount of boron incorporation. The PL linewidths become broader as more boron is introduced into the solid solution.

Improved Procedures for the Generation of Diborane from Sodium Borohydride and Boron Trifluoride

Abstract: Improved procedures for the generation of diborane by the reaction of NaBH4 in triglyme or tetraglyme with the BF3 adducts of di-n-butyl ether, tert-butyl methyl ether, monoglyme, dioxane, and tetrahydropyran were developed. In these systems, generation of diborane requires 2-4 h at 25 degrees C (faster reactions take place at 50 degrees C). The byproduct NaBF4 precipitates from the reaction mixture at 25 degrees C as the reaction proceeds. The high-boiling glyme can be conveniently separated from the lower boiling carrier ethers by simple distillation of the latter. On the other hand, diborane was generated very slowly or not generated using the addition of each of six boron trifluoride-etherates (di-n-butyl ether, tert-butyl methyl ether, tetrahydrofuran, tetrahydropyran, dioxane, and monoglyme) to suspensions of sodium borohydride in the corresponding ether. However, diborane was generated rapidly and quantitatively by the addition of NaBH4 in triglyme (or tetraglyme) to the BF3 adduct of triglyme (or tetraglyme) at room temperature. No solid precipitation occurs during the reaction, making it convenient for large-scale applications. The pure solvent triglyme (or tetraglyme) can be easily recovered and recycled by either crystallizing or precipitating NaBF4 from the generation flask. New procedures for the generation of diborane were also developed by the reaction of NaBF4 with NaBH4 in triglyme (or tetraglyme) in the presence of Lewis acids such as AlCl3 and BCl3.

Kinetic Study of the Diborane/Methylamine Reaction: Composition and Structure of C−B−N Films

Abstract: C−B−N films have been deposited by chemical vapor deposition from methylamine (CH3−NH2) and diborane (B2H6) gas mixtures. For methylamine-rich mixtures (r = [CH3−NH2]/[B2H6] = 6), the deposition reaction is thermally activated, showing a low apparent activation energy (Ea = 7.1 kcal/mol). In gas mixtures with lower methylamine flow rates (r = 1), the reaction is also thermally activated in the 350−550 °C range, the apparent activation energy being slightly higher (16 kcal/mol). In the last case, for temperatures higher than 550 °C the deposition rate decreases at increasing temperatures. At these temperatures, the methylamine is decomposed to methane, ammonia, hydrogen, and hydrogen cyanide, thus changing the deposition reaction. In this temperature range (>550 °C), increasing content of methylamine in the gas mixture produces initially an increase in the deposition rate to a maximum followed by the subsequent decrease for the higher methylamine content. The composition of the deposited films has been ana...

Synthetic routes to cyclic and unsymmetric diborane(4) compounds

Abstract: The reaction between 1,2-B2Cl2(NMe2)2 and disodium catecholate Na2[1,2-O2C6H4] affords the cyclic diborane(4) compound 1,2-B2(NMe2)2(cat) (cat=1,2-O2C6H4), whereas a similar reaction using dilithium thiocatecholate Li2[1,2-S2C6H4] affords the 1,1-isomer 1,1-B2(NMe2)2(thiocat) (thiocat=1,2-S2C6H4). Both compounds can be used to prepare unsymmetric diborane(4) species.

Theoretical Study of the Gas-Phase Reaction of Diborane(3) Anion B2H3-with CO2

Abstract: The complex potential energy surface for the gas-phase ion−molecular reaction of the diborane(3) anion B2H3- with CO2, including 12 [B2H3CO2]- intermediate isomers and 17 interconversion transition states, has been investigated theoretically at the B3LYP/6-311++G(d,p) and single-point CCSD(T)/6-311++G(d,p) levels. The CCSD(T) calculations show that for the B2H3- anion the single-H-bridged isomer HB(H)BH- is thermodynamically 4.7 kcal/mol lower in energy than the kinetically rather unstable nonbridged isomer H2BBH-. The thermodynamical and kinetical stability of these [B2H3CO2]- isomers are determined, and the possible reaction pathways leading to five low-lying dissociation products (A) H3BBO- + CO, (B) c-BH2OBH- + CO, (C) H2BCO- + HBO, (D) H3BCO + BO-, and (E) c-BH2OCH + BO- are probed. It is shown that this reaction is initialized by the nucleophilic attack of B2H3- toward CO2, and all the five products are both thermodynamically and kinetically accessible. Our calculated results for the gas-phase react...

Silicon wafer and method of manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To provide a silicon wafer which is most suitable as an integrated circuit of a semiconductor device having a controlled uniform boron concentration SOLUTION: In the method for manufacturing a silicon wafer, the silicon wafer having boron doped therein is heat treated at a temperature of 1000 degC or more in an atmosphere of a mixture gas of hydrogen and diborane (B2H6) (1) It is desirable to set a mixture ratio of hydrogen in this atmosphere to diborane (B2H6) in a diborane (B2H6) mixture gas at 1% or more In the silicon wafer obtained by the method (1) for manufacturing a silicon wafer, a difference in boron concentration between the outermost surface layer of the wafer and the central part thereof is set at 10% or less (2)

Three sulfur-containing diborane(4) compounds

Abstract: The preparation and structures of three diborane(4) compounds are described. The compound B2(3,4-S2C4H2-1-S)2 [2,2′-bi(1,3,5,2-tri­thia­borapentalene), C8H4B2S6] is planar and lies at a crystallographic inversion centre. The amine adducts [B2(C3S5)2(NHMe2)2] [2,2′-bis­(di­methyl­amino)-2,2′-bi(1,3,4,6,2-tetra­thia­borapentalene-5-thione), C10H14B2N2S10] and [B2(1,2-S2C2H4)2(NHMe2)2]·0.33CH2Cl2 [1,2-bis­(di-methylamino)-1,1:2,2-bis(dimethylenedithioxy)diborane(4) di­chloro­methane solvate, C8H22B2N2S4·0.33CH2Cl2] contain di­methyl­amine ligands bound to each boron in an anti conformation about the B—B bond, with tetrahedral geometry at the B atoms. The crystal structures display a number of S⋯S interactions, which appear to dictate the packing arrangements.

Structure and stability of gold-substituted diborane, boranes, and borohydride ions

Abstract: Pseudopotential ab initio calculations were performed for species of the type BH n (AuPH3) m k , where n+m=3 or 4, and the charge k is −2,…,+1. Some derivatives of these and diaurated diboranes were also studied. The structural data agree well with the available experimental evidence. Factors affecting the stability of these systems, including the role of aurophilic attraction, are discussed. The singly charged anions and the diaurated diboranes are predicted to be the most stable members of these series.

The effect of chlorine on dopant activation in hydrogenated amorphous silicon

Abstract: The dark conductivity of hydrogenated amorphous silicon (a-Si:H) films deposited from dichlorosilane (SiCl2H2) and silane (SiH4), and doped with diborane (B2H6), increases by as much as a factor of 100 over the usual a-Si:H,B films deposited without SiCl2H2. The effect is observed at gas phase concentrations of diborane ranging from 0.006 to 0.5 vol %, and for both direct current (dc) and 13.56 MHz radio frequency plasma depositions, although it is more noticeable for the dc discharge. An increase in dark conductivity is also observed in boron doped hydrogenated amorphous silicon carbon alloys (a-SiC:H) deposited with dichlorosilane, albeit coupled with a change in the Tauc gap. Chlorine reduces the conductivity of undoped and phosphorus doped a-Si:H films. A B–Cl cluster acceptor that is not passivated by H is proposed as a possible mechanism for chlorine enhanced conductivity. This increase in p-layer conductivity translates into an increase of solar cell efficiency, but surprisingly by an increase in p...

Reduction of noxious substances

Abstract: A process for the removal of noxious substances from a gas stream comprises introducing the gas stream and an inorganic hydride (as a reducing agent) into a heated chamber Preferably, the gas stream contains at least one of Cl2, F2, AlCl3, NF3, ClF3, SiCl4, C3F8, and C4F10 The inorganic hydride is typically one or more of silane, diborane, phosphine and ammonia The chamber may be heated to a temperature of between 350°C to 900°C

Change of diborane ion species depending on the magnitude of magnetic field using 100 MHz very high frequency discharge

Abstract: In order to fabricate next generation semiconductor devices, low energy and high current doping ions are required to be transported. In particular the energy of boron ions is required to be less than 1 keV at a current of several mA. When hydrogen-diluted diborane is used as the ion source gas, usually hydrogen ions are also generated as well as borone hydride ions. But if the generation of the hydrogen ions is suppressed, mass separation may be unnecessary. Then the distance between the ion source and the target wafer can be shortened. As a result it becomes easy to transport low energy, high current ion beams. This work is concerned with a new method of plasma production which can suppress the hydrogen ion ratio in the very high frequency (VHF) discharge. We have improved the magnitude of multicusp magnetic field by changing the permanent magnet arrangement at the periphery of the plasma chamber, because the ratio of hydrogen ions strongly depends on the amount of high energy electrons which are produced through a relation between the VHF field and the multicusp field. Optimizing the magnitude of the magnetic field, the ratio of hydrogen ions can be reduced to less than 1% of the total ions.

Improved Procedures for the Generation of Diborane from Sodium Borohydride and Boron Trifluoride.

Abstract: Improved procedures for the generation of diborane by the reaction of NaBH4 in triglyme or tetraglyme with the BF3 adducts of di-n-butyl ether, tert-butyl methyl ether, monoglyme, dioxane, and tetrahydropyran were developed. In these systems, generation of diborane requires 2-4 h at 25 degrees C (faster reactions take place at 50 degrees C). The byproduct NaBF4 precipitates from the reaction mixture at 25 degrees C as the reaction proceeds. The high-boiling glyme can be conveniently separated from the lower boiling carrier ethers by simple distillation of the latter. On the other hand, diborane was generated very slowly or not generated using the addition of each of six boron trifluoride-etherates (di-n-butyl ether, tert-butyl methyl ether, tetrahydrofuran, tetrahydropyran, dioxane, and monoglyme) to suspensions of sodium borohydride in the corresponding ether. However, diborane was generated rapidly and quantitatively by the addition of NaBH4 in triglyme (or tetraglyme) to the BF3 adduct of triglyme (or tetraglyme) at room temperature. No solid precipitation occurs during the reaction, making it convenient for large-scale applications. The pure solvent triglyme (or tetraglyme) can be easily recovered and recycled by either crystallizing or precipitating NaBF4 from the generation flask. New procedures for the generation of diborane were also developed by the reaction of NaBF4 with NaBH4 in triglyme (or tetraglyme) in the presence of Lewis acids such as AlCl3 and BCl3.

Transformation of an unordered structural network in amorphous hydrogenated silicon films as a result of doping with boron

Abstract: The influence of the technological parameters of deposition, the purity and relative concentration of diborane, and the substrate temperature on electrical parameters of (a-Si:H):B films obtained by high-frequency decomposition of a gaseous mixture in a multielectrode system was studied. Simultaneous existence of the mechanisms for doping and modification in the case of introduction of boron from diborane in the course of deposition of (a-Si:H):B films is proposed.

On-line monitoring of boron in dichlorosilane by means of inductively coupled plasma atomic emission spectrometry (ICP-AES)

Abstract: An analytical procedure is described for the determination of boron in dichlorosilane by means of ICP-AES. A modified sampling and gas introduction system allows on-line monitoring of the investigated gas. The calibration of the procedure was carried out by standard additions of gaseous diborane/argon [c(B2H6) = 10.4 µl l−1] and dichlorosilane. The detection limit was found to be 0.63 µg boron g−1 of dichlorosilane.

Synthetic Routes to Cyclic and Unsymmetric Diborane(4) Compounds.

Abstract: The reaction between 1,2-B2Cl2(NMe2)2 and disodium catecholate Na2[1,2-O2C6H4] affords the cyclic diborane(4) compound 1,2-B2(NMe2)2(cat) (cat=1,2-O2C6H4), whereas a similar reaction using dilithium thiocatecholate Li2[1,2-S2C6H4] affords the 1,1-isomer 1,1-B2(NMe2)2(thiocat) (thiocat=1,2-S2C6H4). Both compounds can be used to prepare unsymmetric diborane(4) species.