AVS 66th International Symposium & Exhibition
    Applied Surface Science Division Tuesday Sessions
       Session AS+BI+RA-TuM

Paper AS+BI+RA-TuM6
Practical References for Low Energy Ion Scattering by Ca and F

Tuesday, October 22, 2019, 9:40 am, Room A211

Session: Quantitative Surface Analysis III/Other Surface Analysis Methods
Presenter: Hidde Brongersma, IONTOF Technologies GmbH, Germany/Eindhoven University of Technology, Eindhoven, The Netherlands, Germany
Authors: S. Průsa, Brno University of Technology, Czech Republic
T. Šikola, Brno University of Technology, Czech Republic
H.H. Brongersma, IONTOF Technologies GmbH, Germany/Eindhoven University of Technology, Eindhoven, The Netherlands, Germany
Correspondent: Click to Email
Low-Energy Ion Scattering (LEIS) is known for its extreme surface sensitivity. It is just as well suited for the analysis of amorphous, isolating, extremely rough surfaces, as for flat single crystals. Thus LEIS is applicable to any type of sample that can be taken into vacuum. Since matrix effects are generally absent, or relatively small in LEIS, a quantitative analysis is straightforward. However, the theory to quantitatively predict the atomic sensitivities of the elements falls short. Therefore, an accurate quantification relies on well-defined reference materials. Practical references should be chemically inert, easy to clean and inexpensive. The powder of calcium fluoride, CaF2, has been suggested as practical reference for Ca and F [1], while the powder of calcium carbonate, CaCO3, has also been suggested for Ca [2].

A complication is that the composition of the outer atomic layer of a material is generally fundamentally and radically different from that of the atoms below this surface. Thus it is unlikely that the F/Ca ratio in the outer surface of CaF2 will be 2. In fact, precisely this difference makes the LEIS information unique and complementary to that of analytic techniques such as XPS, Auger and (TOF-) SIMS which probe several to many atoms deep. The difference is also highly relevant, since the outer atoms of a surface largely control important processes as adhesion, catalysis, electron emission and growth

It will be shown how the F/Ca atomic ratio, the Ca and F atomic densities, as well as the roughness factors for CaF2 and CaCO3 have been determined.

[1] T. Gholian Avval, C.V. Cushman, P. Brüner, T. Grehl, H.H. Brongersma, M.R. Linford,

Surf. Sci. Spectra, to be published (2019)

[2] R.M. Almeida, R. Hickey, H. Jain, C.G. Pantano, J. Non-Cryst. Solids 385 (2014) 124