AMBIENT GAS DEPENDENCE OF HYDROGENATED SILICON CLUSTERS GROWN IN AN ION-TRAP

Hydrogenated Si cluster ions have been grown from silane gas under ele ctron irradiation in an ion trap with five different gases, H-2, He, N e, 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 p roduced an exceptionally large amount of Si6Hx+. This dependence was a ttributed to the ability of the ambient gas to dissociate SiH4 to form SiH2 reactant, which is essential to the growth of Si6Hx+.