A MEMS Reactor for Atomic-Scale Microscopy of Nanomaterials Under Industrially Relevant Conditions

Creemer, J.F.; Helveg, Stig; Kooyman, Patricia J.; Molenbroek, A.M.; Zandbergen, H.W.; Sarro, P.M.

doi:10.1109/jmems.2010.2041190

Cited by 107 publications

(80 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the GPL at the edge of the windowed area matched the nominal spacing of 15 µm, the middle of the window bulged to a gas path length of ~50 µm at 760 Torr. Using the approach of Creemer et al 37 , we calculated the atomic density projected along the path of the electron beam through the gas by integrating the molecular density through the thickness of the environmental cell (there will be contributions from both the window membranes and the gas). For O 2 gas at 760 Torr and 300°K with a 50 µm gas path length, this gives a projected density of ~2.5×10 3 atoms/nm 2 due to the gas molecules only.…”

Section: Resultsmentioning

confidence: 99%

A (S)TEM Gas Cell Holder with Localized Laser Heating forIn SituExperiments

Mehraeen

McKeown

Deshmukh³

et al. 2013

Microsc Microanal

View full text Add to dashboard Cite

The advent of aberration correction for transmission electron microscopy has transformed atomic resolution imaging into a nearly routine technique for structural analysis. Now an emerging frontier in electron microscopy is the development of in situ capabilities to observe reactions at atomic resolution in real-time and within realistic environments. Here we present a new in situ gas holder that was designed to bypass several limitations that have plagued previous in situ gas holders. The new holder is compatible with any type of sample, and its capabilities include localized heating and precise control of the gas pressure and composition while simultaneously allowing atomic resolution imaging at ambient pressure. The results show that 0.25 nm lattice fringes are directly visible for nanoparticles imaged at ambient pressure with gas path lengths up to 20 µm. Additionally, we quantitatively demonstrate that while the attainable contrast and resolution decrease with increasing pressure and gas path length, resolutions better than 0.2 nm should be accessible at ambient pressure with gas path lengths less than the 15 µm utilized for these experiments. 3The ability to study gas-solid interactions with atomic resolution and ambient pressures in the transmission electron microscope (TEM) promises new insights into the growth, properties, and functionality of nanomaterials. Heterogeneous catalysis is a particular application in which, the structure, morphology, and chemistry of nanoparticles are dynamic and greatly depend on the gas environment and temperature [1][2][3][4][5][6][7] . Unfortunately, conventional high-resolution TEM of catalysis is extremely challenging since both ambient pressure and elevated temperature can adversely affect imaging conditions. This is further complicated by the fact that normal TEM imaging is performed under a high vacuum (1.5x10 -7 Torr) to prevent unwanted scattering from gases. Therefore, to enable in situ experiments within the column of an electron microscope, a localized gas environmental chamber with controllable gas pressure, composition, and temperature is crucial. Such conditions can be obtained using an environmental cell built around the specimen.The original designs for environmental cells have been around for over 70 years 8 and are produced by either incorporating differentially pumped apertures that separate the specimen from the high vacuum of the TEM column 1, 9-16 or windowed-cell designs that confine the gas within the specimen holder using electron-transparent membranes 4,10,[17][18][19][20][21][22] . Atomic-resolution images in gaseous environments have been obtained with both techniques at pressures up to ~10 Torr 1,5,15,22,23 , but the technological relevance of these measurements may not be compatible with the more realistic operating conditions of catalyst nanomaterials at higher pressures. Environmental transmission electron microscopes (ETEM) that incorporate differentially pumped apertures are generally limited to pressures of 15-20 Torr but they per...

show abstract

Section: Resultsmentioning

confidence: 99%

A (S)TEM Gas Cell Holder with Localized Laser Heating forIn SituExperiments

Mehraeen

McKeown

Deshmukh³

et al. 2013

Microsc Microanal

View full text Add to dashboard Cite

show abstract

“…The presence of a heating system enables the temperature control inside the cell. The reactor is fit into a dedicated specimen holder to position it into the microscope and to connect it with an external gas supply system and a temperature controller [11]. Gas sealing is done with Viton O-rings, which are commonly applied in high vacuum systems.…”

Section: Designmentioning

confidence: 99%

“…In the middle of the channel a 1 × 1 mm 2 freestanding membrane is released to form the reaction chamber and ensure good thermal insulation. The membranes are made of low stress LPCVD SiN [14] and their thickness is 1 μm in order to stand the stress arising from the bulging at a pressure difference of 100 kPa which locally increases the height of the channel up to 35 μm [11]. On the top half, an array of LPCVD TEOS spacers is made in order to prevent the stiction of the two membranes.…”

Section: Designmentioning

confidence: 99%

See 1 more Smart Citation

Wafer-level assembly and sealing of a MEMS nanoreactor forin situmicroscopy

Mele

Santagata

Pandraud

et al. 2010

J. Micromech. Microeng.

View full text Add to dashboard Cite

This paper presents a new process for the fabrication of MEMS-based nanoreactors for in situ atomic-scale imaging of nanoparticles under relevant industrial conditions. The fabrication of the device is completed fully at wafer level in an ISO 5 clean room and it is based on silicon fusion bonding and thin film encapsulation for sealed lateral electrical feedthroughs. The fabrication process considerably improves the performances of previous nanoreactors. The wafer-level assembly allows faster preparation of devices, hydrocarbon contamination is no longer observed and the control of the channel height leads to a better flow reproducibility. The channel is shown to be sufficiently hermetic to work in the vacuum of a transmission electron microscope while a pressure of 100 kPa is maintained inside the nanoreactor. The transparency is demonstrated by the atomic scale imaging of YBCO nanoparticles, with a line spacing resolution of 0.19 nm.

show abstract

“…However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4].…”

mentioning

confidence: 99%

Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

Helveg¹,

Elkjcer²,

Jespersen³

et al. 2018

Microsc Microanal

View full text Add to dashboard Cite

Transmission electron microscopy (TEM) has become indispensable in the study of heterogeneous catalysts. The ability to acquire atomic-resolution images of catalysts opens up for unprecedented new information about the catalyst surface that benefits the understanding of structure-sensitivity in catalysis [1]. However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4]. This nanoreactor is operational with variable gas flows (0-0.1 sccm/min), ambient pressure levels (> 1 bar) and elevated temperatures (25-700 o C), while maintaining the inherent 1Å resolution in modern electron microscopes. Moreover, mass spectrometry of gas exiting the reaction zone is made possible by the small reaction volume of ca. 0.3 nL and reaction calorimetry is accessed from the power compensation used for isothermal operation of the microheater [6].The nanoreactor performance and application will be showcased by observations of Pt nanoparticles under oxidizing and reducing reaction conditions. Specifically, high-resolution TEM images were acquired of the Pt nanoparticles under exposure to reactive gas environments synchronously with mass spectrometry and calorimetry data. Based on such observations, structure-activity relationship will be outlined for e.g. the steady-state and oscillatory catalytic oxidation of carbon monoxide over Pt nanoparticles [6]. These examples demonstrate exciting possibilities for including information about the exposed surface sites into the description of dynamic properties and functions of catalysts.

show abstract

A MEMS Reactor for Atomic-Scale Microscopy of Nanomaterials Under Industrially Relevant Conditions

Cited by 107 publications

References 47 publications

A (S)TEM Gas Cell Holder with Localized Laser Heating forIn SituExperiments

A (S)TEM Gas Cell Holder with Localized Laser Heating forIn SituExperiments

Wafer-level assembly and sealing of a MEMS nanoreactor forin situmicroscopy

Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

Contact Info

Product

Resources

About