Issue 40, 2020

Electron inelastic mean free path in water

Abstract

Liquid phase transmission electron microscopy (LPTEM) is rapidly developing as a powerful tool for probing processes in liquid environments with close to atomic resolution. Knowledge of the water thickness is needed for reliable interpretation and modelling of analytical studies in LPTEM, and is particularly essential when using thin liquid layers, required for achieving the highest spatial resolutions. The log-ratio method in electron energy-loss spectroscopy (EELS) is often applied in TEM to quantify the sample thickness, which is measured relative to the inelastic mean free path (λIMFP). However, λIMFP itself is dependent on sample material, the electron energy, and the convergence and divergence angles of the microscope electronoptics. Here, we present a detailed quantitative analysis of the λIMFP of water as functions of the EELS collection angle (β) at 120 keV and 300 keV in a novel nanochannel liquid cell. We observe good agreement with earlier studies conducted on ice, but find that the most widely used theoretical models significantly underestimate λIMFP of water. We determine an adjusted average energy-loss term Em, water, and characteristic scattering angle θE, water that improve the accuracy. The results provide a comprehensive knowledge of the λIMFP of water (or ice) for reliable interpretation and quantification of observations in LPTEM and cryo-TEM studies.

Graphical abstract: Electron inelastic mean free path in water

Supplementary files

Article information

Article type
Paper
Submitted
08 jun 2020
Accepted
22 jun 2020
First published
30 jun 2020

Nanoscale, 2020,12, 20649-20657

Author version available

Electron inelastic mean free path in water

M. N. Yesibolati, S. Laganá, S. Kadkhodazadeh, E. K. Mikkelsen, H. Sun, T. Kasama, O. Hansen, N. J. Zaluzec and K. Mølhave, Nanoscale, 2020, 12, 20649 DOI: 10.1039/D0NR04352D

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