ION-BEAM SOURCE FOR SOFT-LANDING DEPOSITION

''Soft-landing'' deposition of molecular ions on various surfaces is i mportant in making exotic radicals, modeling electrochemical double la yers, and studying aqueous ion interactions, We have built a new mass- selected ion beam source for soft-landing deposition, designed to prod uce either positive or negative ions, including ions that depend on io n-neutral reactions (e.g., H3O+ and NH4+). The ionizer is a foe jet cr ossed by an electron beam, producing a wide variety of positive and ne gative ions. The simple, short-length, planar ion deceleration minimiz es defocusing and space charge effects. It currently delivers mass-sel ected ions with energies down to about 1 eV and currents of about 10 n A. The design allows easy maintenance. The performance of the ion beam compares favorably with previous low-energy positive ion systems. (C) 1998 American Institute of Physics.