Atomic scale imaging of working membranes

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Atomic scale imaging of operando conditions has been made possible with the development of ultrathin membranes. These membranes allow for the direct observation of atomic processes in real time, providing valuable insights into the behavior of materials under various conditions. This breakthrough has the potential to revolutionize the study of materials science, catalysis, and energy storage, leading to the development of new and improved materials with enhanced properties.

Atomic Scale Imaging: Ultrathin Membranes Revolutionize Microscopy

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Atomic-scale imaging reveals secret to thin film strength

When we think of magnification, we envision either bringing distant objects closer or enlarging tiny objects to a tangible scale. Magnifying instruments, regardless of their scale or direction, have undoubtedly played a pivotal role in the advancement of scientific research. The James Webb Space Telescope (JWST), launched in 2021, embarks on a mission to collect unprecedented data from the deep universe, expanding our understanding of the early universe and the evolution of celestial bodies.

In the atomic realm, the Aberration-Corrected Electron Microscope (ACEM) serves as an analogous tool to the JWST. By harnessing highly coherent electrons and an aberration corrector, the ACEM excels in resolving subatomic features, enabling comprehensive exploration of the structure-functional relationship in materials. As a cornerstone for nanoscale investigations, the modern ACEM provides invaluable information that remains irreplaceable by other characterization methods.

However, the dual nature of high-energy electrons presents a contradiction. While their wave property allows for high-resolution imaging, their particle property makes collisions inevitable. As electrons traverse ambient pressure gas, their mean free path—the distance they can travel before significantly altering their direction or energy—is limited to approximately 100 nm. These collisions disrupt the electron optics, hindering the microscope’s performance.

To circumvent these collisions, the microscope column is typically maintained under ultra-high vacuum conditions, which are at least 1010 times thinner than ambient air. This restriction limits the ACEM’s applicability to static, thin, and solid samples. However, materials exist in various states of matter beyond solids, including liquids, gases, and plasmas. To observe reactions at the nanoscale, encapsulating the fluidic media within a sealed nanoreactor is essential to prevent dissipation.

The utilization of silicon nitride micro-electro-mechanical systems (MEMS) technique addresses these challenges, enabling researchers to explore reactions at the nanoscale. The silicon nitride film, serving as an encapsulation membrane, can be conveniently produced with a thickness in the range of a few tens of nanometers using chemical vapor deposition process. These films exhibit reasonable resilience to mechanical shock, particularly when they exceed a certain thickness, although there is a trade-off relationship with electron transparency.

Analogous to an aquarium with a thick glass wall, which may be robust enough to contain a large amount of water, maximizing visibility through the glass becomes challenging. Therefore, engineering the “wall” is crucial for ensuring optimum visibility in both aquariums and the fluid container for ACEM.

Atomic Scale Imaging: Inspired by Nature: Ultrathin Membranes with Beehive-Like Support

To address this challenge, researchers drew inspiration from the beehive, a structure that withstands high mechanical stress while using minimal material. Their solution involved creating a space-filling hexagonal support system using heavily doped silicon beneath the ultrathin silicon nitride, achieving this with only 1/5th of the thickness of conventional methods. The beehive-like structure maximizes openings for observing reactions and provides optimal strength under mechanical stress.

Through this ultrathin breakthrough, the membrane can be thinned down to a single-digit nanometer scale—approximately 1/10,000th of the thickness of a human hair—without experiencing rupture or leaks in the microscope. The transparency of the ultrathin membrane allows for the mapping of fluids with sub-nanometer spatial resolution and significant suppression of adverse electron scattering, a capability not achievable with conventional enveloping materials.

This breakthrough enables sensitivity in the gas phase to the extent of detecting a handful of gas molecules inside the transmission electron microscope (TEM). This level of sensitivity permits capturing reactions occurring at the gas-solid interface with microsecond-scale time resolution. As an illustrative example, researchers visualized the insertion of hydrogen atoms into palladium metal under ambient temperature and pressure conditions.

This technology holds immense potential for developing and investigating nanocatalysts for gas-phase carbon capture, as well as for energy materials such as fuel cells and metal-air batteries, providing atomic scale insights.

Atomic Scale Imaging: Beyond Nanoscience: Broader Applications of Ultrathin Membranes

The researchers draw a parallel between this development and the groundbreaking capabilities of the James Webb Space Telescope (JWST), which is delivering unprecedented images and data challenging cosmological theories. Furthermore, they propose that this innovative strategy for designing microchips with ultrathin membranes can be extended to various applications where the thin membranes serve as encapsulations and/or support materials, with implications extending beyond the field of nanoscience.

Atomic Scale Imaging: Wrapping Up: A New Frontier in Microscopy and Beyond

The development of ultrathin membranes for in situ/operando microscopy opens up new avenues for exploring materials and reactions at the atomic scale. This breakthrough has the potential to revolutionize fields such as catalysis, energy materials, and environmental science. Beyond nanoscience, the innovative design strategies for ultrathin membranes may find applications in various fields, pushing the boundaries of scientific research and technological innovation..

FAQ’s

1. What is the significance of the Aberration-Corrected Electron Microscope (ACEM) in scientific research?

The ACEM is a powerful tool that enables the study of materials at the atomic scale, providing invaluable information about their structure and properties.

2. What are the limitations of conventional ACEM techniques?

Conventional ACEM techniques are limited to static, thin, and solid samples due to the high-energy electrons’ collisions with ambient pressure gas.

3. How do ultrathin membranes address the limitations of conventional ACEM techniques?

Ultrathin membranes provide a solution by encapsulating the fluidic media within a sealed nanoreactor, preventing dissipation and allowing for the observation of reactions at the nanoscale.

4. What are the advantages of the beehive-like support structure for ultrathin membranes?

The beehive-like support structure maximizes openings for observing reactions, provides optimal strength under mechanical stress, and enables the membrane to be thinned down to a single-digit nanometer scale without rupture or leaks.

5. What are the broader applications of ultrathin membranes beyond nanoscience?

Ultrathin membranes have potential applications in various fields, such as microchip design, encapsulation and support materials, and the study of materials and reactions at the atomic scale.

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