AVS 65th International Symposium & Exhibition
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuA

Invited Paper AS-TuA11
In Situ Liquid SIMS, a Molecular Eye for Examination of Liquids and Liquid Interfaces

Tuesday, October 23, 2018, 5:40 pm, Room 204

Session: The Impact of Modeling (Ion, Electron) and Data Analysis on Applied Surface Science, a Celebration of the Career of Barbara Garrison
Presenter: Zihua Zhu, Pacific Northwest National Laboratory
Authors: Z.H. Zhu, Pacific Northwest National Laboratory
Y. Zhang, Pacific Northwest National Laboratory
Correspondent: Click to Email
Secondary ion mass spectrometry (SIMS) has proven to be a powerful surface analysis tool, because it can provide elemental, isotopic and molecular information with excellent sensitivity and decent spatial resolution. However, SIMS is a high vacuum technique, and it normally is used to analyze solid samples. In recent years, in situ liquid SIMS was developed in my lab with collaboration with Dr. Xiao-Ying Yu, allowing molecular examination of various liquids and liquid interfaces. In brief, an interesting liquid can be sealed within a vacuum compatible device, and a thin silicon nitride (SiN) membrane is used to separate the liquid from vacuum. Then, we use a focused primary ion beam to drill an aperture through the SiN membrane to expose the liquid for SIMS examination. The key design of this idea is the diameter of the aperture: if the diameter is less than 2-3 microns, surface tension of the liquid can hold the liquid without any spraying out. Also, the evaporation from the aperture is controllable, making SIMS measurements fully feasible. If using a cluster primary ion beam, molecular signals from liquid surfaces and solid-liquid interfaces can be readily collected. In situ liquid SIMS has been used to investigate electrode-electrolyte interfaces during electrochemical or electro-catalytic reactions. The uniqueness of this novel approach is simultaneous collection of molecular evolution information of electrode surfaces, reactants, intermediates, and products under operando conditions, offering the possibility to elucidate complicated chemistries occurring at electrode-electrolyte interfaces (e.g., solid-electrolyte interphase in lithium ion batteries). More interestingly, the ionization process of in situ liquid SIMS may be softer than regular electrospray ionization, which is surprisingly different from the traditional opinion that SIMS ionization process is very hard with strong damage. This new finding will shed light on molecular investigation of ion solvation, nucleation before nanoparticle formation, and similar complex processes occurring in liquid environments.