Gas phase ion chemistry in germane/ammonia,methylgermane/ammonia,and methylgermane/phosphine

Gaseous mixtures of germane or methylgermane with ammonia and methylgermane with phosphine have been studied by ion trap mass spectrometry. Rate constants of reactions of the primary ions and of the most important secondary ion species are reported, together with the calculated collisional rate constants and efficiencies of reaction. The GeH_n⁺ (n = 0–3) ions, formed by electron ionization of both GeH₄ and CH₃GeH₃, react with ammonia yielding, among others, the GeH_n⁺ (n = 2–4) ion family, which, in a successive and slow reaction with NH₃, only give the unreactive ammonium ion. Also, the CH₃GeH_n⁺ (n = 1, 2) species do not form Ge–N bonds, whereas secondary ions of germane, such as Ge₂H₂⁺, produce species containing germanium and nitrogen together. In the CH₃GeH₃/PH₃ mixture a great number of ions are formed with rather high rate constants from primary ions of both reagent molecules and from phosphorus containing secondary ions. GePH_n⁺ (n = 2–4) ions further react with methylgermane leading to cluster ions with increasing size such as Ge₂PH_n⁺ and Ge₂CPH_n⁺. The experimental conditions favoring the chain propagation of ions containing Ge and N, or Ge and P, with or without C, important in the chemical vapor deposition of materials of interest in photovoltaic technology, are discussed.