a An Ar Gas Cluster Ion Beam (GCIB) has been shown to remove previous Ar + ion beam-induced surface damage to a bulk polyimide (PI) film. After removal of the damaged layer with a GCIB sputter source, XPS measurements show minor changes to the carbon, nitrogen and oxygen atomic concentrations relative to the original elemental bulk concentrations. The GCIB sputter depth profiles showed that there is a linear relationship between the Ar + ion beam voltage within the range from 0.5 to 4.0 keV and the dose of argon cluster ions required to remove the damaged layer. The rate of recovery of the original PI atomic composition as a function of GCIB sputtering is similar for carbon, nitrogen and oxygen, indicating that there was no preferential sputtering for these elements. The XPS chemical state analysis of the N 1s spectra after GCIB sputtering revealed a 17% damage ratio of altered nitrogen chemical state species. Further optimization of the GCIB sputtering conditions should lead to lower nitrogen damage ratios with the elemental concentrations closer to those of bulk PI.

We have applied sputtering using a buckminsterfullerene (C 60 ) ion beam for XPS analysis. A practical sputter rate of 2.4 nm min −1 for SiO 2 was obtained for sputtering an area of 5 mm × 5 mm using a 5 kV C 60 ion beam with an energy of 83 eV per carbon atom. Extremely low sputtering degradation of polytetrafluoroethylene was observed in these conditions. The results were compared with argon ion beam energies of 500 V and 5 kV. These are the first results utilizing a C 60 ion beam for XPS analysis with limited sputtering damage.

Three-dimensional (3D) chemical images reveal the surface and subsurface distribution of pharmaceutical molecules in a coronary stent coating and are used to visualize the drug distribution as a function of elution time. The coronary stent coating consists of 25% (w/w) sirolimus in a poly(lactic-co-glycolic acid) (PLGA) matrix and is spray-coated onto metal coupons. Information regarding the 3D distribution of sirolimus in PLGA as a function of elution time was obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging using a Au(+) ion beam for analysis in conjunction with a C(60)(+) ion beam for sputter depth profiling. The examined formulation is shown to have large areas of the surface as well as subsurface channels that are composed primarily of the drug, followed by a drug-depleted region, and finally, a relatively homogeneous dispersion of the drug in the polymer matrix. Elution is shown to occur from the drug-enriched surface region on a relatively short time scale and more gradually from the subsurface regions of homogeneously dispersed drug. Bulk composition was also probed by X-ray photoelectron spectroscopy (XPS) depth profiling and confocal Raman imaging, the results of which substantiate the TOF-SIMS 3D images. Finally, the effectiveness of a C(60)(+) ion beam for use in 3D characterization of organic systems is demonstrated against another polyatomic ion source (e.g., SF(5)(+)).