Liquid thickness estimation in transmission electron microscopy

Transmission electron microscopy has become a valuable tool for time-resolved characterization of nano-scale materials during exposure to liquid environments. As the imaging resolution and contrast depends on liquid thickness, measurements and control of the liquid phase are of critical importance. While the log-ratio method in electron energy-loss spectroscopy (EELS) has been demonstrated for estimating the thickness of thin liquid layers, this method becomes unreliable for liquid layers, with log-ratio measures larger than 4. Herein, we demonstrate that the energy position of the multiple scattering peak can be calibrated to be used as an alternative thickness measure of thicker samples in both broad-beam and focused-beam illumination conditions. With this approach it is shown that in addition to unavoidable window bulging of the silicon nitride window membranes, the silicon chips can also bulge when clamped in the liquid holder which gives rise to additional liquid thickness and means to suppress this unwanted effect are demonstrated.