| AVS 60th International Symposium and Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoA |
| Session: | Analyses Using Novel Ion Beams |
| Presenter: | J. Matsuo, QSEC, Kyoto University, CREST, Japan |
| Authors: | J. Matsuo, QSEC, Kyoto University, CREST, Japan S. Nakagawa, Kyoto University, CREST, Japan M. Fujii, QSEC, Kyoto University, CREST, Japan T. Aoki, Kyoto University, CREST, Japan T. Seki, Kyoto University, CREST, Japan |
| Correspondent: | Click to Email |
Following the development of novel primary ion beams, such as SF5, C60, Bi3, and Arn, material analysis with secondary ion mass spectrometry (SIMS) has been widely used for organic and biological materials. In particular, with such ion beams the time-of-flight (TOF) SIMS system can provide whole mass spectra for the determining molecular structures on surfaces, and very recently these beams have been used in molecular depth profiling to investigate multilayer structures consisting of various organic materials. Thus, TOF-SIMS is considered to be an important surface analysis technique for organic and biological materials. Furthermore, mass spectrometric imaging with high lateral resolution can be achieved with the TOF-SIMS technique, because ion beams are easily focused down to submicrometer dimension.
However, there are still numerous challenges in applying TOF-SIMS to real biological samples. For instance, to compete with other mass spectrometry techniques, such as MALDI, DESI, DART, PADI, etc., mass resolution and sensitivity are expected to be improved. We have demonstrated that massive Ar cluster beams are quite useful as a primary beam in SIMS. Because of the high-density energy deposition and multiple collisions with low energy atoms on the surface, there are much less fragmented ions in the SIMS spectra of large organic materials. This is one of the advantages of massive Ar cluster beams, because many biological samples are crude and contain many similar but different molecules. For instance, when di-stearoyl-phosphatidyl-choline (DSPC), which is generally the most abundant lipid in animal cell membranes, is measured with SIMS, fragmented ions (184 Da) as well as protonated secondary molecular ions (791 Da) are detected. The ratio of fragmented ions to molecular ions measured with massive Ar cluster beams is around 10, which is two orders lower than the ratio measured with Bi3 ion beam. One of the technical problems of massive Ar cluster beams was the difficulty of obtaining a short-pulsed beam, because of the large mass distribution. We have developed a TOF-SIMS mass spectro meter system with ortho gonal acceleration (oa-TOF), which allo ws use of a continuous beam. The mass resolution of this system is better than 16,000, which is comparable to the conventional SIMS with pulsed ion beams.
The latest results of massive Ar cluster SIMS will be presented and discuss ed in comparison with other techniques.
Acknowledgements
This work is supported by the Core Research of Evolutional Science and Technology (CREST) of JST.
J. Matsuo,S. Ninomiya, H. Yamada, K. Ichiki, Y. Wakamatsu, M. Hada, T. Seki and T. Aoki, Surf. Inter face Anal . ( 2011 ) 42, 1612