The development and extensive use of spherical aberration (Cs) correction systems in the TEM has helped to achieve an unprecedented level of spatial resolution with low to intermediate voltage (up to 300 kV) microscopes. The combination of TEMs and aberration correction systems has enabled the discovery of new properties of materials at the atomic scale.
For in situ experiments, the resolving power of these microscopes will undoubtedly lead to new discoveries when materials are subjected to stimuli such as external electric fields or high temperature. The Protochips Fusion heating and electrical biasing system has been developed to provide an ultra stable and low-drift platform for conducting high-resolution imaging at high temperatures.
This article outlines an experiment that shows how the full resolution capability of the TEM can be achieved with Fusion at high temperatures.
The TEAM 0.5 TEM was used to perform the experiment at the National Center for Electron Microscopy (NCEM) at the Lawrence Berkeley National Laboratory (LBNL). It is an FEI Titan cubed with probe and image Cs correctors (CEOS), a monochromator, and a bright X-FEG electron source.
The TEAM 0.5 TEM can resolve to 0.5 Å in conventional TEM mode and was operated at 300 kV during this experiment. Gold was directly evaporated on an E-chip™, which produced small gold nanoparticles directly on the E-chip™. It provides good scattering and contrast needed for resolution tests.
A phase-contrast image of a gold nanoparticle at 600 °C is shown in Figure 1A. At this temperature, lattice fringes and the typical 5-fold faceting and twinning characteristics of gold nanoparticles can be seen clearly.
As illustrated in Figure 1B, the Fast Fourier transform (FFT) shows that a 0.6 Å resolution was achieved at 600 °C. This resolution is close to the TEM resolution limit of 0.5 Å, indicating that Fusion does not limit the TEM resolution even at this temperature.
Figure 1. Gold nanoparticle at 600 °C with the corresponding FFT
As the temperature was increased from room temperature to 600 °C, the nanoparticles became increasingly dynamic. These particles began to coalesce, facets were altered, and defects in the material became mobile. The system’s stability enabled imaging, including the recording of real-time movies and analysis of these events at the atomic scale, with unprecedented clarity.
A stable, low drift heating system is required by conventional and aberration corrected TEMs to fully exploit their resolution capabilities for analytical and imaging analysis. The Fusion heating and electrical biasing system allows atomic resolution imaging and analysis of materials, and can be used on all materials for in situ heating.
This information has been sourced, reviewed and adapted from materials provided by Protochips.
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