Micro-fabricated channel with ultra-thin yet ultra-strong windows enables electron microscopy under 4-bar pressure

Abstract

Transmission electron microscopy (TEM) of (de-)hydrogenation reactions is crucial to characterize efficiency of hydrogen storage materials. The nanoreactor, a micromachined channel with 15-nm-thick windows, effectively confines the gas flow to an electron-transparent chamber during TEM of reactions. Realistic experiments require very high pressures to be sustained by the device. Nanomechanical bulge tests and simulations show that due to a very strong size effect, ultra-thin device components can reliably withstand tensile stresses as high as 19.5 GPa enabling high pressure operation. We use the device to characterize Pd particles under a 4-bar H 2 pressure within the ultra-high-vacuum of the TEM. The increasing demand in alternative, clean energy sources has attracted a considerable attention to hydrogen as energy carrier and nanostructured metal hydrides as potential hydrogen storage materials.

Advances in windowed gas cells for in-situ TEM studies

“…Some groups just used their newly developed windowed cells to demonstrate their properties and improved technical limits for in-situ TEM observations [1,20,23,54,56]. This section will discuss these applications in details.…”

“…Alan et al [56] designed a MEMS-type nanoreactor whose geometry differed slightly from the earlier version [18,19,54]. This nanoreactor (Figure 4(d)) consisted of two micro-machined parts brought into contact to form a channel.…”

“…(c) [55]: An electron micrograph showing a close-up of the as-prepared Pt nanoparticles framed in (b). (d) [56]: Schematic of the MEMS nanoreactor. (e) [56]: close-up view of a particle enclosed between two circular electron transparent windows implemented in the new generation device.…”

“…(e) [56]: close-up view of a particle enclosed between two circular electron transparent windows implemented in the new generation device. (f) [56]: stress distribution within the 1.2 mmthick central square plate containing circular windows under 4 bar pressure difference, calculated by finite element simulations. all sides by SiN x and could be resistively heated to 500 1C over a prolonged period of time.…”

In situ and operando transmission electron microscopy of catalytic materials

“…The group at the Technical University of Delft first demonstrated atomic resolution of 0.18 nm at pressures above 1 atmosphere and temperatures up to 500 o C (13). Recent results show that controlled atmosphere experiments with windowed cells can be performed at pressures up to 4 atmospheres and elevated temperatures (14,15). The issue of temperature measurement when gas of variable pressure and composition is introduced is an ongoing challenge in the MEMS based windowed cells.…”