AC Impedance Measurement and Electron Holography of Ionic Liquid in a Transmission Electron Microscope

Abstract

Alternating current (AC) impedance measurements were performed with ionic liquid (IL) specimens to study feasibility of in-situ characterization method for conductive and dielectric properties of materials in a transmission electron microscope (TEM). A bridge-shaped IL specimen was prepared between two molybdenum (Mo) probe tips in a TEM, and was exposed to electron beam. The repeated AC impedance measurements during the irradiation revealed that the conductance of the IL bridge decreased faster at higher frequencies. Electron holography around the IL before and after the electron irradiation revealed enhanced charging after the irradiation, which is consistent with the loss of conductance by the irradiation. AC impedance measurement and electron holography are compatible with TEM to complementarily provide dynamic transport properties and potential distribution of a specimen.

Time-resolved electron holography and its application to an ionic liquid specimen

“…To evaluate the capability of T-R EH in characterizing the dynamic response of materials, we used an ionic conductor as the target material. Ionic liquids (ILs), a class of ionic conductors, possess low vapor pressure compatible with a specimen chamber for electron microscopy, and EH observations of ILs have been reported with image acquisition by conventional continuous exposures [ 19 , 20 ]. An IL, N,N,N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) imide [ 21 ] was used.…”