Exploring the environmental transmission electron microscope

Wagner, Jakob Birkedal; Cavalca, Filippo; Damsgaard, Christian Danvad; Duchstein, Linus Daniel Leonhard; Hansen, Thomas Willum

doi:10.1016/j.micron.2012.02.008

Cited by 87 publications

(68 citation statements)

References 37 publications

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“…However, it is often necessary to study materials in situ within their operating environment; catalysts, for instance, may evidence very different exposed surfaces in a gas environment than in the high vacuum environment of a typical TEM [1,2]. Dedicated environmental TEMs (ETEM) can allow high resolution imaging and spectroscopy in a gaseous environment, but are limited to mbar-range pressures [3][4][5][6]. To simulate operando conditions for many relevant systems, higher pressures are needed: the decomposition temperature of PdO in O 2 , for instance, changes by nearly 300 degrees between 1 mbar and 1 atm [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

et al. 2015

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Environmental transmission electron microscopy (TEM) has enabled in situ experiments in a gaseous environment with high resolution imaging and spectroscopy. Addressing scientific challenges in areas such as catalysis, corrosion, and geochemistry can require pressures much higher than the ∼20 mbar achievable with a differentially pumped environmental TEM. Gas flow stages, in which the environment is contained between two semi-transparent thin membrane windows, have been demonstrated at pressures of several atmospheres. However, the relationship between the pressure at the sample and the pressure drop across the system is not clear for some geometries. We demonstrate a method for measuring the gas pressure at the sample by measuring the ratio of elastic to inelastic scattering and the defocus of the pair of thin windows. This method requires two energy filtered high-resolution TEM images that can be performed during an ongoing experiment, at the region of interest. The approach is demonstrated to measure greater than atmosphere pressures of N2 gas using a commercially available gas-flow stage. This technique provides a means to ensure reproducible sample pressures between different experiments, and even between very differently designed gas-flow stages.

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Section: Introductionmentioning

confidence: 99%

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

et al. 2015

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“…For example, while contracting the beam at a constant total dose-rate has no effect on the resolution, it will increase the extent of beam-induced changes to the sample as these are reported to be determined primarily by the areal dose-rate [26][27][28][29][30]. Conversely, expanding the electron beam puts surrounding areas at risk for unintentional exposure and structural alterations.…”

Section: Resultsmentioning

confidence: 99%

On the role of the gas environment, electron-dose-rate, and sample on the image resolution in transmission electron microscopy

Jespersen

Damsgaard

et al. 2016

Adv Struct Chem Imag

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The introduction of gaseous atmospheres in transmission electron microscopy offers the possibility of studying materials in situ under chemically relevant environments. The presence of a gas environment can degrade the resolution. Surprisingly, this phenomenon has been shown to depend on the electron-dose-rate. In this article, we demonstrate that both the total and areal electron-dose-rates work as descriptors for the dose-rate-dependent resolution and are related through the illumination area. Furthermore, the resolution degradation was observed to occur gradually over time after initializing the illumination of the sample and gas by the electron beam. The resolution was also observed to be sensitive to the electrical conductivity of the sample. These observations can be explained by a charge buildup over the electron-illuminated sample area, caused by the beam-gas-sample interaction, and by a subsequent sample motion induced by electrical capacitance in the sample.

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“…The effect of a gas phase on TEM imaging sensitivity and resolution has been a subject of recent studies (Yoshida and Takeda, 2005;Jinschek and Helveg, 2012;Wagner et al, 2012;Bright et al, 2013;Suzuki et al, 2013). The differentially pumped cell, as implemented on the FEI Titan 80-300 ETEM, can accommodate gas environments at pressures of 10 −5 mbar-20 mbar, corresponding to a diatomic gas path for the electron beam of up to 75 atoms/Å 2 (Jinschek and Helveg, 2012).…”

Section: Enabling Atomic-scale Sensitivity and Resolution In In Situ mentioning

confidence: 99%

Observing gas-catalyst dynamics at atomic resolution and single-atom sensitivity

Helveg

Kisielowski

Jinschek³

et al. 2015

Micron

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Transmission electron microscopy (TEM) has become an indispensable technique for studying heterogeneous catalysts. In particular, advancements of aberration-corrected electron optics and data acquisition schemes have made TEM capable of delivering images of catalysts with sub-Ångström resolution and single-atom sensitivity. Parallel developments of differentially pumped electron microscopes and of gas cells enable in situ observations of catalysts during the exposure to reactive gas environments at pressures of up to atmospheric levels and temperatures of up to several hundred centigrade. Here, we outline how to take advantage of the emerging state-of-the-art instrumentation and methodologies to study surface structures and dynamics to improve the understanding of structure-sensitive catalytic functionality. The concept of using low electron dose-rates in TEM in conjunction with in-line holography and aberration-correction at low voltage (80 kV) is introduced to allow maintaining atomic resolution and sensitivity during in situ observations of catalysts. Benefits are illustrated by exit wave reconstructions of TEM images of a nanocrystalline Co3O4 catalyst material acquired in situ during their exposure to either a reducing or oxidizing gas environment.

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Exploring the environmental transmission electron microscope

Cited by 87 publications

References 37 publications

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

On the role of the gas environment, electron-dose-rate, and sample on the image resolution in transmission electron microscopy

Observing gas-catalyst dynamics at atomic resolution and single-atom sensitivity

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