Gas-phase ion chemistry of the propyne/ammonia and silane/propyne/ammonia systems

Abstract

Ion/molecule reactions in the C 3H 4/NH 3 and SiH 4/C 3H 4/NH 3 gaseous mixtures were investigated by ion trap mass spectrometry, with the aim of finding the best experimental conditions for formation and growth of ion clusters containing silicon, carbon and nitrogen. These species may play an important role in the deposition of silicon carbides doped with nitrogen by X-ray assisted chemical vapour deposition methods from suitable systems. In the study of the C 3H 4/NH 3 mixture the main reaction pathways leading to formation of C/N-containing species were identified. Few mixed C/N ions are formed, with low formation rates, and their overall abundance reaches only 7% of the total ion current after 1 s reaction time. In the ternary mixture, mixed Si-containing ions were found to be the most efficient precursors of ternary ion species. The SiC n H q + ( n=1–3; q=2–5, 7) ions efficiently react with ammonia, but only in few cases these reactions lead to formation of ternary mixed ions as hydrocarbon loss mostly occurs with formation of binary SiNH q + ( q=2, 4) ions. On the other hand, propyne was found to be very reactive and several ternary mixed ions were formed from its reactions with SiNH q + ( q=2, 4) and SiCNH q + ( q=6, 8) ions. The total abundance of ternary mixed ions reaches 20% of the total ion current after 1 s reaction time.