Ion/molecule reactions in SiH4/H2S and GeH4/H2S mixtures

The gas phase ion chemistry of silane/hydrogen sulfide and germane/hydrogen sulfide mixtures was studied by ion trap mass spectrometry (ITMS), in both positive and negative ionization mode. In positive ionization, formation of X/S (X = Si, Ge) mixed ions mainly takes place via reactions of silane or germane ions with H2S, through condensation followed by dehydrogenation. This is particularly evident in the system with silane. On the other side, reactions of HnS2+ ions with XH4 (X = Si, Ge) invariably lead to formation of a single X–S bond. In negative ionization, a more limited number of mixed ion species is detected, but their overall abundance reaches appreciable values, especially in the SiH4/H2S system. Present results clearly indicate that ion processes play an important role in formation and growth of clusters eventually leading to deposition of amorphous solids in chemical vapor deposition (CVD) processes.