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Spatial Resolution in Scanning Electron Microscopy and Scanning Transmission Electron Microscopy Without a Specimen Vacuum Chamber

Published online by Cambridge University Press:  25 July 2016

Kayla X. Nguyen*
Affiliation:
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
Megan E. Holtz
Affiliation:
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
Justin Richmond-Decker
Affiliation:
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
David A. Muller
Affiliation:
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, USA
*
*Corresponding author.[email protected]
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Abstract

A long-standing goal of electron microscopy has been the high-resolution characterization of specimens in their native environment. However, electron optics require high vacuum to maintain an unscattered and focused probe, a challenge for specimens requiring atmospheric or liquid environments. Here, we use an electron-transparent window at the base of a scanning electron microscope’s objective lens to separate column vacuum from the specimen, enabling imaging under ambient conditions, without a specimen vacuum chamber. We demonstrate in-air imaging of specimens at nanoscale resolution using backscattered scanning electron microscopy (airSEM) and scanning transmission electron microscopy. We explore resolution and contrast using Monte Carlo simulations and analytical models. We find that nanometer-scale resolution can be obtained at gas path lengths up to 400 μm, although contrast drops with increasing gas path length. As the electron-transparent window scatters considerably more than gas at our operating conditions, we observe that the densities and thicknesses of the electron-transparent window are the dominant limiting factors for image contrast at lower operating voltages. By enabling a variety of detector configurations, the airSEM is applicable to a wide range of environmental experiments including the imaging of hydrated biological specimens and in situ chemical and electrochemical processes.

Type
Technique and Instrumentation Development
Copyright
© Microscopy Society of America 2016 

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