Ambient gas dependence of hydrogenated silicon clusters grown in an ion trap

Hydrogenated Si cluster ions have been grown from silane gas under electron irradiation in an ion trap with five different gases, H-2, He, Ne, Ar and Xe, as ambient. The mass spectra of Si6Hx+ always had three peaks corresponding to x = 1, 7 and 13, but their peak heights varied depending on the ionization energy of the ambient gas except that Hp produced an exceptionally large amount of Si6Hx+. This dependence was attributed to the ability of the ambient gas to dissociate SiH4 to form SiH2 reactant, which is essential to the growth of Si6Hx+.