Jiro Matsuo oral presentation (RM-Thu2-2-5)
Observation of Adsorption and Desorption of Water Molecules with Ambient SIMS
1 Quantum Science and Engineering Center, Kyoto University, Gokasho, 611-001 Uji, Japan
2 SENTAN, Japan Science and Technology Agency (JST), Chiyoda, 102-0075 Tokyo, Japan
Water has a rather high vapor pressure (>1000 Pa), and phenomena of absorption and desorption of water molecules on and from solid surfaces are often observed. The physical and chemical properties of the water molecule and its surface, as well as water in liquid state and its interface with solids are an interesting field of study. However, because of the high vapor pressure of water, the use of conventional surface and interface analytical techniques that require high vacuum conditions is not possible. Moreover, most liquids are organic materials for which chemical analysis is more important than elemental analysis. Thus, for the study of water and its interface with solids, a new analytical technique that works in ambient conditions is strongly required.
We have developed a secondary ion mass spectrometry technique with swift (high-energy >MeV) heavy ion beams (MeV-SIMS) and found that secondary molecular ion emission was significantly enhanced with swift heavy ion beams . Furthermore, these ion beams have a high transmission capability in matter and can be extracted under ambient conditions. This “Ambient SIMS” technique can provide unique information on liquid surfaces and solid–liquid interfaces . A 6-MeV Cu ion beam was introduced into a target chamber that was kept at ambient conditions (100,000 Pa) with varying humidity levels (0–100%). Secondary molecular ions were emitted from the sample surface and were extracted through a small orifice (100 μm diameter) into a differentially pumped chamber and measured with orthogonal acceleration time-of-flight (oa-TOF) mass spectrometer, as shown Fig. 1. Ambient SIMS spectra of a Si wafer obtained with swift heavy ions under wet and dry conditions are shown in Fig. 2. In the wet condition, water clusters indicating a liquid water layer were found.
Recent progress on this technique will be presented and discussed along with possible applications for liquid analysis.
 J. Matsuo, S. Ninomiya, H. Yamada, K. Ichiki, Y. Wakamatsu, M. Hada, T. Seki, T. Aoki, Surf. Interface Anal., 42, 1612 (2010)
 M. Kusakari, M. Fujii, T. Seki, T. Aoki, J. Matsuo, J. Vac. Sci, and Tech. B, 34, 034H111, (2016)