The X-ray photoelectron spectroscopic (XPS) analysis of thin film or multilayer organic materials has recently been improved by the introduction of cluster ion sources for sputter depth profiling. One such commercially available cluster ion source uses the polyaromatic hydrocarbon (PAH) coronene. This source has successfully produced useful depth profiles of a number of model polymer films [1] [2] and mixed organic systems. [3] Results demonstrate a significant reduction in ion induced damage, as measured by XPS between ion etch sputter cycles, compared with conventional ion sources. High ion yields have been found for several polymers including poly(lactic-co-glycolic acid) (PLGA); Polyacrylic acid (PAA); and polylactic acid (PLA), however, other polymers, such as polystyrene (PSS), appear to be resistant to sputter profiling using cluster ion sources under previously investigated conditions. [4]

In this study we investigate a range of experimental parameters which influence ion yields and surface damage with the aim of optimising sputtering conditions for a number of different organic materials. Experimental factors include incident ion energy; ion beam angle of incidence; and sample temperature.

 

[1] D.E. Weibel, N. Lockyer, J.C. Vickerman, App. Surf. Sci., 2004, 231-232, 146-152.

[2] A.J. Roberts, S.J. Hutton, C.J. Blomfield, I. Drummond, S.C. Page, J. Surf. Anal., 2009, 3, 287.

[3] A. Rafati, M.C. Davies, A.G. Shard, S. Hutton, G. Mishra, M.R. Alexander, J. Controlled Release, 2009, 138, 40–44

[4] R. Mollers, N. Tuccitto, V. Torrisi, E. Niehuis, A. Licciardello, Applied Surface Science 2006, 252, 6509-6512.