Energies of Cu 1+ ions sputtered from Cu by very low energy (50 eV < E < 1 keV) Inert gas ions

Abstract

He +, Ne + and Ar + ions with energies E 1 between 50 and 1000 eV were used to bombard a polycrystalline Cu target at an angle of 45°. The energies, E 2, of the Cu 1 + ions sputtered at 90° to the primary beam were investigated using a UHV magnetic sector mass spectrometer. The maxima of the energy distributions as measured by the instrument, were at values of E 2 of about 4 eV (±1 eV), nearly independent of e 1 and primary ion mass. Plots of log N( E 2) versus log E 2 displayed limited linear portions over which the functional dependence of N( E 2) is proportional to E 2 −0.5. Plots of the average secondary ion energy, Ē 2, versus the energy transferred by the primary ion to a Cu atom in a direct collision ([ 4m 1m 2 (m 1 + m 2) 2 ]E 1) , indicate that Ē 2 increases linearly with transfer energy up to a transferred energy of about 200 eV, independent of primary ion mass. Above about 200 eV transferred energy, Ē 2 asymptotically approaches values which depend upon primary ion mass. At transferred energies below about 200 eV, the collision kinematics in the fust few collisions appears to dominate the emission process.