MEMS‐based nanoreactor for in situ analysis of solid–gas interactions inside the transmission electron microscope

Abstract

A nanoreactor-based system for in situ analysis of solid-gas interactions inside the transmission electron microscope, referred to as the 'climate system', is introduced here. The latter uses an micro-electro mechanical systems (MEMS)-based device as a multi-functional sample carrier and microsized laboratory for simultaneous heating and gas experiments. To assemble the nanoreactor, two chips are sandwiched together to form a minimised chemical reaction chamber. The bottom chip contains a four-point-probe microheater, which controls and introduces the heating environment (up to 1300°C) around the sample. Similarly, it contains the spacers that define the height of the gas chamber. The top chip confines the gas in the microchamber while isolating it from the external environment. Both chips contain electron transparent windows that allow the electron beam to pass through for in situ imaging. The sample can be deposited or prepared directly on the windows, which are made of silicon nitride and can sustain pressures up to 1.5 bar and high temperatures while ensuring low background atomic resolution imaging.

Liquid phase transmission electron microscopy with flow and temperature control

“…The Nano-Cell relies on the dual-chip concept of sandwiching two MEMS devices to seal a miniaturized chamber, 48 Figure 1b shows the architecture of the MEMS devices that form the Nano-Cell. These MEMS devices are consumable sample carriers, which can be replaced to prevent cross contamination between experiments.…”

“…The metal heating coil resistance is linearly dependent on the temperature, which allows for simultaneous heating and accurate temperature measurement 56. In this way the software is able to control the temperature via a closed loop feedback algorithm, similar to our previous efforts for in situ heating in vacuum or gas 48,57. In this case the heater is not located on a membrane close to the imaging area but on the silicon substrate instead(Figure 2).…”

In Situ Local Temperature Mapping in Microscopy Nano‐Reactors with Luminescence Thermometry

“…The monolithic reactor, described in Figure c, claims to have an accurate and local temperature control (up to 800 °C) and can reach up to 14 bar, which comes close to industrially relevant conditions. A second type is the dual‐chip nano‐reactor, in which two chips are aligned on top of each other to create the gas channel, sealed by O‐rings . In these reactor types, it is much easier to place catalyst particles, but their pressure range is typically limited to 1 bar.…”

“…Microelectromechanical systems (MEMS) nano‐reactors have been developed over the last decade to satisfy these requirements. For the STXM experiments described in literature, two generations of nano‐reactor can be distinguished.…”

Advanced In Situ TEM Microchip with Excellent Temperature Uniformity and High Spatial Resolution

“…Therefore, it is imperative to choose appropriate materials that can withstand harsh conditions and provide accurate results when conducting transmission electron beam imaging experiments. To prevent this from happening, materials with a small coefficient of thermal expansion that are compatible with MEMS manufacturing technology, such as amorphous silicon nitride, are used [33,34]. By employing such materials, researchers can accurately observe the sample's behavior under various conditions, allowing for a more in-depth understanding of the material's properties and reactions.…”