Electronic sputtering of carbon clusters from ion beam irradiated organic films

Abstract

Positive ions of even numbered carbon clusters C+2n (n > 20) are ejected as a result of the interaction of fast MeV ions with poly(vinylidene fluoride) (PVDF). Experiments provide circumstantial evidence that these ejected carbon clusters have a three-dimentional structure, consisting of pentagons and hexagons, i.e. they are fullerenes. We have studied the effect of macroscopic carbonisation induced by ion bombardment on the ejection of carbon cluster ions (C+n, n = 1–33; C+2nn = 21–50) from PVDF. Damage cross-section values are extracted from the fluence dependence of the secondary ion yields. The yield of fullerene ions from PVDF decreases as a function of MeV ion fluence. Accordingly, macroscopic carbonisation of the polymer is detrimental and is not a prerequisite to fullerene emission, confirming earlier findings that these carbon clusters are formed and ejected in a single MeV ion impact basis. For comparison, the sputtering of carbon cluster ions originating from films of poly(tetrafluorethylene), poly(styrene), poly(ethylene terephthalate) and fluorinated fullerene have also been studied.