Energy distributions of neutral atoms sputtered by very low energy heavy ions

Abstract

Polycrystalline Cu was sputtered by normally incident, very low energy Ar + ions ( E 0 = 40–1000 eV). The kinetic energy ( E) distributions of the neutral Cu atoms sputtered normally from the Cu surface were measured, using secondary neutral mass spectrometry. For values of E 0 above approximately 600 eV, the observed energy distributions agreed closely with the Thompson-Sigmund theory. For values of E 0 less than about 600 eV the distributions fell off faster than predicted by the Thompson-Sigmund theory, and the peak value of the distribution shifted to somewhat lower energies. Both these effects were exaggerated as E 0 was further lowered. The average kinetic energy of the sputtered neutral Cu atoms increased with increasing E 0. The rate of this increase was less at higher values of E 0.