Molybdenum and Carbon Cluster Angular Sputtering Distributions Under Low Energy Xenon Ion Bombardment

Molybdenum and carbon cluster (C 2 and C 3) angular sputtering distributions are measured during xenon ion bombardment from a plasma, with incident ion energy EXe ranging between 50 and 225 eV. A quadrupole mass spectrometer (QMS) is used to detect the fraction of sputtered neutrals that is ionized in the plasma, and to obtain the angular distribution by changing the angle between the target and the QMS aperture. The angular sputteri ng distribution for molybdenum presents a maximum at 60°, and this maximum becomes less pronounced as the incident ion energy increases. The dependence of the total sputtering yield on incident ion energy is in good agreement with previous experiments. The re is a large increase of about two orders of magnitude in the sputtering yield from EXe = 50 to 125 eV, and a more moderate increase for higher energies. Sputtered C 2 and C 3 clusters exhibit a similar angular sputtering distribution with a maximum at appr oximately 45 -60°; however, this maximum becomes more pronounced for higher incident energies, in contrast to the molybdenum case. The angular distribution of the sputtered clusters depends on the energy with which they are ejected. The low energy populatio n of sputtered particles has a broad maximum at 45°, while the high energy population has a sharp maximum at 60°. The cluster sputtering yield monotonically increases by less than one order of magnitude from EXe = 50 to 225 eV for all measured sputtering a ngles except for normal sputtering, which has a maximum yield at EXe� 100 eV.