Continuous Mass Selected Cluster Ion Production using a Liquid Metal Ion Source
A continuous source of mass-selected cluster ions is highly desirable for investigations requiring large numbers of clusters. An apparatus capable of producing a variable energy DC beam of mass-selected cluster ions and landing them on a solid substrate has been developed based on a liquid metal ion source. Clusters emitted from such a source into a cone of approximately eight degrees half-angle are focused by a multiple-element electrostatic lens into a nearly parallel beam and mass separated by a 60 degree magnetic sector to resolve individual cluster species. A second electrostatic lens/decelerator focuses the mass-resolved beam through a 0.125 inch diameter gridded aperture. The ion energy at this point is variable and can range from 0 to 2000 eV, and collection of clusters on a solid substrate is possible with landing energies ~20 eV or less. Characterization of the transport of clusters through the system is described. In addition, preliminary results have been obtained for collection of cluster ions on silicon surfaces.
KeywordsLine Intersection Convolution Gallium Active Element
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