Highly Unsaturated Hydrogenated Silicon Clusters, SinHx (n = 3−10, x = 0−3), in Flash Pyrolysis of Silane and Disilane

Abstract

Bare and partially hydrogenated neutral silicon clusters, SinHx (n = 3−10, x = 0−3), were produced upon flash pyrolysis of dilute (1%) mixtures of disilane, Si2H6, in Ar and of silane, SiH4, in He at temperatures above ∼1000 K. Immediately following the flash pyrolysis of the precursors (on an ∼20 μs time scale), the clusters were isolated in a supersonic molecular beam and detected by single vacuum ultraviolet (VUV) photon (λ = 118.2 or 121.6 nm) ionization time-of-flight mass spectrometry (TOFMS). The clusters produced were similar for both precursors with SinHx (n = 4, 6, 7, 10) being significantly populated and Si6Hx being the most abundant, consistent with the known “magic numbers” of Si clusters. Hydrogen contents in these SinHx clusters were small with typical hydrogen mole fractions near 10%. The most stable structures of the Si6H and Si6H2 clusters were identified using ab initio quantum mechanical methods. Initial thermal decomposition intermediates and reaction products, such as SiH2, Si2H4, Si...