Comparison of xenon and gallium sources on the detection and mapping of lithium in Li-containing materials by using ToF-SIMS combined FIB-SEM.

Abstract

Li can find itself a wide range of applications since it is the lightest metal. However, Li detection by microscopy-based techniques is problematic because of the highly susceptible nature during electron beam irradiation. ToF-SIMS is a versatile technique to detect Li but the detection of light materials is also problematic due to the large ion contaminated zone and low sputtering yield. By combining ToF-SIMS with a recently launched Xe ion source FIB-SEM, which has small ion contamination and high sputtering yield features, can produce more realistic data at near surface and below the surface region especially for the detection of lightweight materials such as Li. In this study, Li detection and mapping capabilities of ToF-SIMS attached to the FIB-SEM with Ga and Xe ion sources were discussed for Al incorporated Li7 La3 Zr2 O12 solid electrolyte sample that contains Li and Al rich regions at triple junctions. In spite of smoother milling from Ga source, Xe performs more precisely in Li mapping. Low ion contaminated zone, high sputtering yield and low straggling obtained from Monte Carlo simulations are the main advantages of Xe ion sources. The Li detection efficiency for Xe is higher than Ga source discriminating the LiAlO2 phase placed at the triple junctions of grains and La2 Zr2 O7 regions placed at the outer side of LLZO neighbouring the LiAlO2 phase. LAY DESCRIPTION: Li can find itself a wide range of applications since it is the lightest metal. However, Li detection by microscopy-based techniques is problematic because of the highly susceptible nature during electron beam irradiation. ToF-SIMS is a versatile technique to detect Li but the detection of light materials is also problematic due to the large ion contaminated zone and low sputtering yield. By combining ToF-SIMS with a recently launched Xe ion source FIB-SEM, which has small ion contamination and high sputtering yield features, can produce more realistic data at near surface and below the surface region especially for the detection of lightweight materials such as Li. In this study, Li detection and mapping capabilities of ToF-SIMS attached to the FIB-SEM with Ga and Xe ion sources were discussed for Al incorporated Li7 La3 Zr2 O12 solid electrolyte sample that contains Li and Al rich regions at triple junctions. In spite of smoother milling from Ga source, Xe performs more precisely in Li mapping. Results were also supported from Monte Carlo simulations of ion-atom interactions. The Li detection resolution of xenon is much higher than gallium source discriminating the LiAlO2 phase placed at the triple junctions of grains and La2 Zr2 O7 regions placed at the outer side of LLZO neighbouring the LiAlO2 phase.