It is well-known that radiation damage caused by fast electrons in the electron microscopes is a main obstacle for high resolution transmission electron microscopy (HRTEM) characterisation of materials that are easily damaged by the exposure to electrons. Although extensive research has been carried out on damage mechanisms, critical doses, and low-dose imaging techniques for decades, the search for the ultimate resolution for radiation-sensitive materials imaging and the most optimal imaging conditions is still continuing.
Due to the usually simultaneous existence of more than one kind of damage mechanism and the innate complexity of each damaging process, theoretical predictions of the dose-limited resolution for many materials are still only qualitative. When it comes to the design of quantitative low-dose experiments, whether it is single-shot imaging or image series acquisition, a more accurate knowledge of the effects of dose rate, total dose, accelerating voltage and microscope aberrations on the resolution is needed to achieve the optimal resolution for a particular sample.
In this work we demonstrate an experimental approach to determining the dose-limited resolution of radiation-sensitive materials. Apart from the established low-dose imaging methods, we apply multiple related techniques, such as exit wave reconstruction and non-rigid image registration to improve the quantitative data analysis and interpretation. It is shown that with careful calibration, the suggested quantitative low-dose high resolution imaging and data processing procedures should be easily adaptable to any specific transmission electron microscope equipped with standard instrumentation.