Gas phase ion/molecule reactions in phosphine/germane mixtures studied by ion trapping

Abstract

Gaseous mixtures of phosphine and germane have been investigated by ion trap mass spectrometry. Reaction pathways together with rate constants of the main reactions are reported. The mechanisms of ion/molecule reactions have been elucidated by single and multiple isolation steps. The GeH n + ( n = 1–3) ions react with phosphine to give GePH n + ( n = 2–4) ions. The GePH 4 + ion further reacts with GeH 4 to yield Ge 2PH 6 +. The GePH n + ( n = 2–4) mixed ionic family also originates from the P + phosphine primary ion, as well as from the P 2H n + ( n = 0–3) secondary ions of phosphine reacting with neutral germane and from Ge 2H 2 + reacting with phosphine. The main reaction pathways of the PH n + ( n = 0–2) ions with GeH 4 lead to the formation of the GeH 2 + and GeH 3 + ionic species. Protonation of phosphine from different ionic precursors is a very common process and yields the stable phosphonium ion, PH 4 +. Trends in total abundances of secondary GePH n + ( n = 2–4) ions as function of reaction time for different PH 3/GeH 4 pressure ratios show that excess of germane slightly affects the nucleation of mixed Ge-P ions.