The relative abundances of silicon hydride clusters, SinHx− (n = 8–12 and 0 ≤ x ≤ 25), investigated with high-resolution time-of-flight mass spectrometry

Results are presented of a high-resolution time-of-flight mass spectrometric study on large silicon hydride cluster anions, SinHx− (where n = 8–12, 0 ≤ x ≤ 25). The clusters were produced via the reactions between a dilute silane gas mixture and a laser-induced transition metal plasma. Extensive degrees of hydrogenation were observed for larger Sin− clusters, with an onset appearing around Si8− and continuing on into the Si12− series. The relative abundances of the majority isotopes constituting a precise mass were completely analyzed allowing qualitative assessments of the stability for a particular SinHx− cluster to be ascertained. The SinHx− clusters are observed to possess varying abundances depending on the extent of hydrogenation and the number of silicon atoms constituting the cluster. Specific clusters, which exhibited enhanced stability in the molecular beam, are Si8H6−, Si8H8−, Si9H5−, Si11H2− and Si12H2−, respectively. In general, the lighter SinHx− (n = 8–10) clusters were dominated by high relative abundances of the pure silicon cluster parent, Si8–10−, and the singly hydrogenated cluster, Si8–10H−. A pronounced decrease in intensity was then noted with one additional H adsorption, forming the di-hydride species, Si8–10H2−. The exact converse was observed in the heavier silicon hydride series, SinHx− (n = 11–12), where the pure silicon cluster parent, Si11–12−, and single hydrogenation species, Si11–12H− are suppressed by a substantial production of an especially stable Si11–12H2− di-hydride moiety.

The relative stabilities of large silicon hydride clusters are quantified by implementing an isotopic deconvolution of high-resolution time-of-flight mass spectra.Figure optionsDownload high-quality image (61 K)Download as PowerPoint slide