Er. Fuoco et al., Surface analysis studies of yield enhancements in secondary ion mass spectrometry by polyatomic projectiles, J PHYS CH B, 105(18), 2001, pp. 3950-3956
In this paper we examine the mechanism of secondary ion yield enhancements
previously observed for polyatomic projectiles by measuring the weight loss
, volume loss, and surface composition of poly(methyl methacrylate) (PMMA)
films sputtered by keV SF5+ and Ar+ projectile ions. The sputter yield-the
amount of material removed from the surface by 3.0 keV SF5+ projectiles-was
found to be 2.2 +/- 0.8 higher than for Arf projectiles, measured by weigh
t loss in the PMMA film with a quartz crystal microbalance. This result is
consistent with sputter yield measurements reported here using 5.5 keV ions
and stylus profilometry, Thus, the > 10x enhancement in secondary ion yiel
d in secondary ion mass spectrometry observed for polyatomic ion projectile
s is not attributable to the modest similar to 2x enhancements observed in
the sputter yields for this molecular solid. Surface chemical measurements
by X-ray photoelectron spectroscopy also indicated fundamental differences
in atomic versus polyatomic sputtering mechanisms at 3.0 keV, but not at 0.
7 keV. These results provide a reasonable explanation for the depth profili
ng capability demonstrated here on PMMA films for 5.5 keV SF5+ ions that is
not possible with isoenergetic Ar+ ions.