title: Experimental and modeling studies of B atom number density distributions in hot filament activated B2H6/H2 and B2H6/CH4/H2 gas mixtures.
abstract: Experimental and modeling studies of the gas-phase chemistry occurring in dilute, hot filament (HF) activated B2H6/H2 and B2H6/CH4/H2 gas mixtures are reported. Spatially resolved relative number densities of B (and H) atoms have been measured by resonance enhanced multiphoton ionization methods, as a function of process conditions (e.g. the HF material and its temperature, the B2H6/H2 mixing ratio, and the presence (or not) of added CH4). Three-dimensional modeling of the H/B chemistry prevailing in such HF activated gas mixtures using a simplified representation of the gas phase chemistry succeeds in reproducing all of the experimentally observed trends, and in illustrating the key role of the "H-shifting" reactions BHx + H <= => BHx-1 + H2 (x = 1-3) in enabling rapid interconversion between the various BHx (x = 0-3) species. CH4 addition, at partial pressures appropriate for growth of boron-doped diamond by chemical vapor deposition methods, leads to approximately 30% reduction in the measured B atom signal near the HF. The modeling suggests that this is mainly due to concomitant H atom depletion near the HF, but it also allows us a first assessment of the possible contributions from B/C coupling reactions upon CH4 addition to HF activated B2H6/H2 gas mixtures.
authors.affiliation: School of Chemistry, University of Bristol, Bristol, U.K.
authors.forename: Dane W
authors.initials: DW
authors.lastname: Comerford
authors.forename: Andrew
authors.initials: A
authors.lastname: Cheesman
authors.forename: Thomas P F
authors.initials: TP
authors.lastname: Carpenter
authors.forename: David M E
authors.initials: DM
authors.lastname: Davies
authors.forename: Neil A
authors.initials: NA
authors.lastname: Fox
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Sage
authors.forename: James A
authors.initials: JA
authors.lastname: Smith
authors.forename: Michael N R
authors.initials: MN
authors.lastname: Ashfold
authors.forename: Yuri A
authors.initials: YA
authors.lastname: Mankelevich