Gas‐phase ion chemistry in the ternary SiH₄–C₃H₆–NH₃ system

Abstract

The gas-phase ion chemistry of propene-ammonia and silane-propene-ammonia mixtures was studied by ion trap mass spectrometry. As far as the binary mixture is concerned, the effect of different molar ratios of the reactants on the trend of ion species formed was evaluated, the ion-molecule reaction processes were identified and the rate constants for the main processes were measured. The results were compared with the collisional rate constants to determine the reaction efficiencies. In the ternary silane-propene-ammonia mixture the mechanisms of formation of Si(m)C(n)N(p)H(q)(+) clusters were elucidated and the rate constants of the most important steps were measured. For some species, selected by double isolation (MS/MS), the low abundance of the ions allowed us to determine the reaction paths but not the rate constants. Ternary ions are mainly formed by reactions of Si(m)C(n)H(q)(+) ions with ammonia, whereas a minor contribution comes from reactions of Si(m)N(p)H(q)(+) ions with propene. On the other hand, the C(n)N(p)H(q)(+) ions showed a very low reactivity and no step leading to ternary ion species was identified. The formation of hydrogenated ternary ions with Si, C and N has a basic importance in relation to their possible role as precursors of amorphous silicon carbides doped with nitrogen obtained by deposition from silane-propene-ammonia mixtures properly activated.

Gas‐phase ion chemistry in XH4C3H4ZH3 (XSi, Ge; ZN, P) mixtures

“…The germane–propyne–phosphine mixture is more reactive than the analogous system with ammonia, in agreement with what was observed for the ternary systems of germane, ethene and ammonia or phosphine, respectively 18. However, it is important to note that, when ternary systems of silane, a hydrocarbon and ammonia or phosphine are compared,13–16 the nitrogen‐containing systems are more reactive, in contrast to what happens to the systems with germane. The simplest conclusion that can be drawn is that silicon has a higher affinity for nitrogen than for phosphorus, the opposite occurring for germanium.…”

“…Mass spectrometry (MS) is a powerful tool for this kind of investigation, as it has been successfully applied to the study of the overall reactivity of gaseous systems and the determination of reaction sequences and kinetics of selected ions 9–12. In our laboratory, ion–molecule reactions occurring in ternary mixtures of silane (silane–propene–phosphine,13 silane–propene–ammonia,14 silane–propyne–ammonia,15 silane–propyne–phosphine16 and silane–allene–phosphine17) were studied previously. As far as germane is concerned, we have investigated the GeH 4 C 2 H 4 XH 3 (XN, P) systems 18.…”

“…Helium buffer gas was supplied by SIAD at an extra‐high purity grade and was used without further purification. All the experiments were run on a Finnigan (Austin, TX, USA) ion trap MS (ITMS) instrument maintained at 333 K in order to obtain results comparable to those from previous studies 12–21. Pressures were measured by a Bayard Alpert ion gauge and corrected for both the relative sensitivity ( S r ) of the ion gauge with respect to different gases ( S r (allene) = 2.3169; S r (ammonia) = 1.112; S r (germane) = 1.937; S r (helium) = 0.19; S r (phosphine) = 1.975; S r (propyne) = 2.1609; S r (silane) = 1.697) (M. Decouzon, J.F.…”

Gas‐phase reactions of SiHn+ (n = 1,2) with NF3: A computational investigation on the detailed mechanistic aspects

“…[1] Thus, over the years, the gasphase ion chemistry of binary and ternary mixtures containing SiH 4 and hydrogen, [2] hydrocarbons, [3][4][5][6][7][8][9][10][11][12][13][14][15][16] water, [17] inorganic oxides, [18,19] ammonia, [20][21][22][23][24] phosphine, [25][26][27][28][29] and halocarbons [30][31][32] was investigated by various experimental and theoretical methods. [1] Thus, over the years, the gasphase ion chemistry of binary and ternary mixtures containing SiH 4 and hydrogen, [2] hydrocarbons, [3][4][5][6][7][8][9][10][11][12][13][14][15][16] water, [17] inorganic o...…”

“…The gas-phase reactions of the cationic silicon hydrides SiH n þ (n ¼ 0-3) are of interest for fundamental reasons, and also to appreciate the role of ionic processes in the chemical vapor deposition of electronic and optoelectronic materials from gaseous mixtures containing SiH 4 . [1] Thus, over the years, the gasphase ion chemistry of binary and ternary mixtures containing SiH 4 and hydrogen, [2] hydrocarbons, [3][4][5][6][7][8][9][10][11][12][13][14][15][16] water, [17] inorganic oxides, [18,19] ammonia, [20][21][22][23][24] phosphine, [25][26][27][28][29] and halocarbons [30][31][32] was investigated by various experimental and theoretical methods. More recently, ion trap mass spectrometry (ITMS) and ab initio calculations were used to study the reactions occurring in ionized mixtures of SiH 4 and NF 3 .…”