Paper AS-TuM9
3D Analysis of Organic Multilayer Structures by TOF-SIMS Using Ar Cluster Ions

Tuesday, November 1, 2011, 10:40 am, Room 102

Organic multilayer systems are of increasing importance in many technological fields. The entry of the OLED technology into commercially available multi-color displays is one example. Optimization of this technology in terms of lifetime and efficiency requires a detailed knowledge of the layer and interface composition.

From the analytical point of view, theses OLED multilayer structures are quite challenging. A detailed analysis requires the identification of complex high mass organic molecules in thin layers of only several nanometer thickness with a lateral resolution in the micrometer range. In particular the identification of the molecular composition is challenging for SIMS as molecular information does usually not survive high dose sputtering conditions.

In the past different projectiles such as low energy Cs⁺ [1] and keV C₆₀⁺ cluster [2-4] have been explored for their depth profiling capabilities on organic layers. For some materials molecular information survives but for the majority of organic molecules depth profiling using these projectiles fails. Recently the application of large Ar clusters for the non-destructive removal of organic matter has been discussed in the SIMS community. The GCIB (gas cluster ion beam) technique was developed by the group of Isao Yamada [5] at the University of Kyoto and has already demonstrated some potential in this field of application [6].

We used a TOF.SIMS 5 instrument equipped with a Bi cluster ion gun for the analysis and an Ar GCIB as well as an C₆₀ cluster ion gun providing both analysis and sputter gun capabilities. In this contribution we will focus on the variation of the sputter projectile, the energy dependence of the resulting depth resolution and the survival of specific molecular ion signal under high dose sputtering conditions. For this purpose a well-defined multilayer model sample similar to a working OLED device was used. The knowledge about the optimum analysis conditions gained on the model system was transferred to a 3D analysis of an OLED display device using an Ar GCIB for sputtering.

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