EMISSION-ANGLE INTEGRATED YIELDS OF NEUTRAL CLUSTERS IN SUB-KEV-ENERGY SPUTTERING

Using spherical samples of copper and nickel, emission-angle integrated yields of neutral atoms, dimers and trimers were determined for normal incidence Ar+ bombardment at energies from 30 to 1000 eV by means of sputtered-neutral mass spectrometry. For both elements, yields of dimers and trimers are proportional over more than two orders of magnitude to the atomic yields squared and cubed, respectively. These correlations are indicative of cluster formation via a combinative association of individually sputtered atoms upon their passage through the surface barrier. The importance of emission-angle integrated multimer yields in low-energy sputtering is emphasized by a comparison with the respective data obtainted for a limited emission angle from planar samples.