Positive ion chemistry of SiH_4 3/NF_3 gaseous mixtures studied by ion trap mass spectrometry

摘要

The positive ion chemistry occurring in silaneitrogen trifluoride gaseous mixtures has been investigated by ion trap mass spectrom_etry. Reaction sequences and rate constants have been determined for the processes involving the primary ions SiH_n~+ (n=0-3) and NF_x~+ (x=1-3) and the secondary ions obtained from their reactions with SiH_4 and NF_3. The SiH_n~+ efficiently react with NF_3 and undergo cas_cades of abstraction and scrambling reactions which form the fluorinated and perfluorinated cations SiHF_m~+ (m=1, 2), SiH_2F~+ and SiF_x~+ (x=1-3). Fluorinated Sit-clusters such as Si_2H_2F~+, Si_2H_3F~+ and Si_2H_5F~+ were also observed. The reaction of both SiH3* and SiH_2F~+ with NF_3 produces the elusive fluoronitrenium ion NHF~+ Any NF_x~+ reacts with SiH_4 mainly by charge transfer. Additional ionic products are, however, observed which suggest intimate reaction complexes. Worth mentioning is the formation of SiNH2* from the reaction of both NF~+ and NHF~+ with SiH_4. The primary ions NF_2~+ and SiH_3~+ are also "sink" species in our observed chemistry.