BHCl₂ Formation during Chemical Vapor Deposition of Boron in a Dual-Impinging Jet Reactor

Abstract

Chemical vapor deposition (CVD) of boron from BCl3 and H2 was investigated in a dual-impinging jet reactor which was connected to an FT-IR spectrometer for on-line chemical analysis of the reactor outlet stream. Formation of the intermediate, BHCl2, during CVD of boron on a hot tungsten substrate was experimentally verified. Boron deposition started at substrate temperatures of around 750 °C and showed a significant deposition rate increase with an increase in temperature. At a surface temperature of 1350 °C, fractional conversion of BCl3 to B and BHCl2 was found to be around 0.6 and 0.2, respectively. At temperatures less than 1100 °C, fractional conversion of BCl3 to BHCl2 was found to be higher than the fractional conversion to boron. Formation of BHCl2 occurs in the gas phase even at temperatures lower than 750 °C. Contribution of surface reactions to the formation of BHCl2 increases with an increase in temperature.

Development of polymer‐molding‐releasing metal mold surfaces with perfluorinated‐group‐containing polymer plating

“…The analysis of the FTIR spectra revealed the existence of HCl and BHCl 2 in addition to hydrogen and boron trichloride, which are consistent with the previous studies 6, 11. IR absorption bands of boron trichloride and HCl were observed between 865 and 1055 cm −1 and 2500 and 3135 cm −1 , respectively.…”

“…Boron fibre can be produced using the chemical vapor deposition technique, with the reaction of BCl 3 or other boron halides with hydrogen gas on a hot metal substrate 2–7. In this process, mass transfer, surface reaction, and gas phase reaction kinetics affect the boron deposition rate on the hot substrate 8–10.…”

Understanding the CVD process of (Si)–B–C ceramics through FTIR spectroscopy gas phase analysis

“…These authors have shown the presence of HBCl2 in the reactor for a temperature as low as 350°C. Moreover, such a species had already been evidenced by FTIR for the BCl3-H2 system [33][34][35] and by mass spectrometry for the BCl3-TiCl4-H2 system [36][37] .…”

A review on the methods of preparation of elemental boron

“…Chemical vapor deposition involving the reduction of boron halides (BCl 3 or BBr 3 ) by hydrogen over a hot substrate is the dominating technique for the production of elemental boron . The major concerns in this process are usually the purity, conversion rate, morphology, and the deposition rate of the produced boron.…”

“…This is majorly due to the significance of diffusion resistance in the parallel flow reactor. In this CVD reactor, diffusion of BCl 3 to the heated substrate surface plays an important role on the deposition rate; even at higher temperatures, a larger amount of BCl 3 is converted into BHCl 2 in the gas phase within the thermal boundary layer adjacent to the substrate, while such transport effects are minimized in the impinging jet reactors, which results in the high fractional conversion of BCl 3 to B than that of BCl 3 to BHCl 2 .…”