| AVS 54th International Symposium | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoA |
| Session: | Quantitative Surface Analysis II. Electron Spectroscopies: (Honoring the contributions of Martin Seah, NPL, and Cedric Powell, NIST) |
| Presenter: | B. Hagenhoff, Tascon GmbH, Germany |
| Authors: | D. Breitenstein, Tascon GmbH, Germany R. Kersting, Tascon GmbH, Germany B. Hagenhoff, Tascon GmbH, Germany R. ter Veen, Calipso B.V., The Netherlands H. Brongersma, Calipso B.V., The Netherlands |
| Correspondent: | Click to Email |
Low Energy Ion Scattering (LEIS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) enable the analysis of the atomic and chemical surface composition of vacuum sustainable samples. Applying LEIS, the surface of a sample is hit by noble gas ions (He+, Ne+, ...) of low energy (1-5 keV). Elastic collisions with individual surface atoms can cause backscattering of the projectiles. Analyzing the energy of these scattered noble gas ions, and moreover knowing their mass and initial energy, the identity of the atomic collision partner can be calculated. Therefore, LEIS enables the quantitative determination of the elemental composition of the samples‘ outermost monolayer. Ions scattered in deeper layers, loose extra energy along the in- and outgoing trajectories. This is used to obtain non-destructive high-resolution depth profiles (0-10 nm). In ToF-SIMS the surface of the samples is also bombarded with atomic - or even polyatomic - projectiles. In contrast to LEIS the energy (10-25 keV) and the mass (e.g. Bi3+: 627 u) of these projectiles is relatively high. The impact of these projectiles leads to a formation of collision cascades in surface near regions resulting in a desorption of particles (electrons, neutral and ionized atoms as well as molecules). The ions can be mass separated and detected in a ToF analyzer providing elemental and molecular information on the first 1-3 surface monolayers. Both techniques provide useful information on the surface composition of solids. However, this information differs for LEIS and ToF-SIMS in several aspects: Firstly, LEIS offers the lower information depth. Whereas ToF-SIMS probes the uppermost three monolayers, LEIS generates information on the outermost monolayer. Secondly, ToF-SIMS offers information on the elemental as well as molecular composition of the surface, whereas with LEIS solely elemental information can be obtained. Furthermore, in terms of quantification, LEIS is superior to ToF-SIMS. Finally, ToF-SIMS allows a laterally resolved probing of the sample down to a resolution of 100 nm whereas in LEIS the lateral resolution is restricted to 0.1-1 mm. This paper compares results of applying LEIS as well as ToF-SIMS to well-defined samples such as Langmuir-Blodgett monolayers but also to analytically relevant samples like nanoparticles. It will highlight the strengths of both techniques and the synergism obtained in applying both methods.