TY - JOUR
T1 - A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope
AU - Colby, R.
AU - Alsem, D. H.
AU - Liyu, A.
AU - Kabius, B.
N1 - Funding Information:
This work was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national science user facility sponsored by the Department of Energy's Office of Biological and Environmental Research , and located at Pacific Northwest National Laboratory. The authors would also like to acknowledge the support of the EMSL William Wiley Post-doctoral Fellowship , and assistance of the Materials Characterization Lab at Penn State University for followup tests. Thanks are extended to L. Kovarik for a number of helpful discussions, and to Roar Kilaas for updates to MacTempas that simplified defocus measurement.
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/6/1
Y1 - 2015/6/1
N2 - 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 ~20mbar 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.
AB - 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 ~20mbar 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.
UR - http://www.scopus.com/inward/record.url?scp=84924326131&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84924326131&partnerID=8YFLogxK
U2 - 10.1016/j.ultramic.2015.01.002
DO - 10.1016/j.ultramic.2015.01.002
M3 - Article
C2 - 25765435
AN - SCOPUS:84924326131
SN - 0304-3991
VL - 153
SP - 55
EP - 60
JO - Ultramicroscopy
JF - Ultramicroscopy
ER -