Antonino Licciardello oral presentation (OB1-Thu2-1-5)
Molecular depth profiling of polymers by NO-assisted sputtering with energetic Cs ions
University of Catania, Viale Andrea Doria, 6, 95125 Catania, Italy
Sputtering of organic materials by high energy monoatomic primary beams causes profound rearrangements and modifications inside the sample, due to ion-beam induced “damage” processes. It is well known that, due to these processes, most of the chemical information in organic matter is lost and the in-depth information is limited to the elemental distribution only. Also, changes in density and sputtering yield can occur, introducing additional complications in data interpretation. Although, nowadays, most of the above issues have been overcame by the introduction of GCIBs, different approaches have been proposed, aiming to solve – at least partly – the problem of ion-induced chemical damage under monoatomic beam irradiation. In particular, Houssiau demonstrated the possibility of obtaining molecular depth profiles of polymers by using ultra-low energy Cs+ ions , thanks to the inhibition of radical reactions by the reactive cesium accumulating at the sample surface. A similar inhibition process allows the improvement, by means of Nitric Oxide gas dosing, of C60-based depth profiles of challenging polymers.
Although, presently, the performances of GCIBs for depth profiling of organics/polymers remain unparalleled, the use of “damaging” sputter beam conditions - in combination with processes that can partly inhibit the beam-induced chemical damage - can provide useful information about ion-beam induced reactions occurring during depth profiling, that are still largely unclear. Moreover, from the point of view of applications, the use of heavy monoatomic sputter beams could provide some advantage in terms of sputter yield uniformity and/or depth resolution in the case of hybrid samples.
In this context, we present some recent results on molecular depth profiling of polymers by NO-assisted sputtering with Cs ion beams with energy of a few keV. The effect of primary ion energy, NO partial pressure, polymer molecular weight and film thickness on the sputter yield and quality of depth profiles will be discussed.
 L. Houssiau, N. Mine (2010), Surf. Interface Anal., 42, 1402–1408
 R. Havelund, A. Licciardello, J. Bailey, N. Tuccitto, D. Sapuppo, I. S. Gilmore, J. S. Sharp, J. L. S. Lee, T. Mouhib, A. Delcorte (2013) Analytical Chemistry, 85, 5064-5070