Editing Electron (section)

=== Imaging ===
[[Low-energy electron diffraction]] (LEED) is a method of bombarding a crystalline material with a [[Collimated light|collimated beam]] of electrons and then observing the resulting diffraction patterns to determine the structure of the material. The required energy of the electrons is typically in the range 20–200&nbsp;eV.<ref>
{{cite book
 | last = Oura | first = K.
 | title = Surface Science: An Introduction
 | pages = 1–45
 | publisher = [[Springer Science+Business Media]] | year = 2003
 | isbn = 978-3-540-00545-2
 |display-authors=etal
}}</ref> The [[reflection high-energy electron diffraction]] (RHEED) technique uses the reflection of a beam of electrons fired at various low angles to characterize the surface of crystalline materials. The beam energy is typically in the range 8–20&nbsp;keV and the angle of incidence is 1–4°.<ref>
{{cite book
 | last1 = Ichimiya
 | first1 = A.
 | last2 = Cohen
 | first2 = P.I.
 | title = Reflection High-energy Electron Diffraction
 | page = 1
 | publisher = Cambridge University Press
 | year = 2004
 | isbn = 978-0-521-45373-8
 | url = https://books.google.com/books?id=AUVbPerNxTcC&pg=PA1
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084445/https://books.google.com/books?id=AUVbPerNxTcC&pg=PA1
 | url-status = live
}}</ref><ref>
{{cite journal
 | last = Heppell | first = T.A.
 | year = 1967
 | title = A combined low energy and reflection high energy electron diffraction apparatus
 | journal = [[Measurement Science and Technology|Journal of Scientific Instruments]]
 | volume = 44 | issue = 9 | pages = 686–688
 | doi =10.1088/0950-7671/44/9/311
 | bibcode = 1967JScI...44..686H
}}</ref>

The [[electron microscope]] directs a focused beam of electrons at a specimen. Some electrons change their properties, such as movement direction, angle, and relative phase and energy as the beam interacts with the material. Microscopists can record these changes in the electron beam to produce atomically resolved images of the material.<ref>
{{cite web
 | last = McMullan
 | first = D.
 | title = Scanning Electron Microscopy: 1928–1965
 | publisher = University of Cambridge
 | year = 1993
 | url = https://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm
 | access-date = 2009-03-23
 | df = dmy-all
 | archive-date = 2009-03-16
 | archive-url = https://web.archive.org/web/20090316071650/http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm
 | url-status = live
}}</ref> In blue light, conventional [[optical microscope]]s have a diffraction-limited resolution of about 200&nbsp;nm.<ref>
{{cite book
 | last = Slayter
 | first = H.S.
 | title = Light and electron microscopy
 | page = 1
 | publisher = Cambridge University Press
 | year = 1992
 | isbn = 978-0-521-33948-3
 | url = https://books.google.com/books?id=LlePVS9oq7MC&pg=PA1
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084446/https://books.google.com/books?id=LlePVS9oq7MC&pg=PA1
 | url-status = live
}}</ref> By comparison, electron microscopes are limited by the [[Matter wave|de Broglie wavelength]] of the electron. This wavelength, for example, is equal to 0.0037&nbsp;nm for electrons accelerated across a 100,000-[[volt]] potential.<ref>
{{cite book
 | last = Cember
 | first = H.
 | title = Introduction to Health Physics
 | pages = 42–43
 | publisher = [[McGraw-Hill|McGraw-Hill Professional]]
 | year = 1996
 | isbn = 978-0-07-105461-4
 | url = https://books.google.com/books?id=obcmBZe9es4C&pg=PA42
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084443/https://books.google.com/books?id=obcmBZe9es4C&pg=PA42
 | url-status = live
}}</ref> The [[Transmission Electron Aberration-Corrected Microscope]] is capable of sub-0.05&nbsp;nm resolution, which is more than enough to resolve individual atoms.<ref>
{{cite journal
 |last1           = Erni
 |first1          = R.
 |display-authors = etal
 |year            = 2009
 |title           = Atomic-Resolution Imaging with a Sub-50-pm Electron Probe
 |journal         = [[Physical Review Letters]]
 |volume          = 102
 |issue           = 9
 |page            = 096101
 |doi             = 10.1103/PhysRevLett.102.096101
 |bibcode         = 2009PhRvL.102i6101E
 |pmid            = 19392535
 |osti = 960283
 |url             = https://digital.library.unt.edu/ark:/67531/metadc927376/
 |access-date     = 2018-08-17
 |archive-date    = 2020-01-02
 |archive-url     = https://web.archive.org/web/20200102164706/https://digital.library.unt.edu/ark:/67531/metadc927376/
 |url-status      = live
}}</ref> This capability makes the electron microscope a useful laboratory instrument for high resolution imaging. However, electron microscopes are expensive instruments that are costly to maintain.

Two main types of electron microscopes exist: [[Transmission electron microscopy|transmission]] and [[scanning electron microscope|scanning]]. Transmission electron microscopes function like [[overhead projector]]s, with a beam of electrons passing through a slice of material then being projected by lenses on a [[Reversal film|photographic slide]] or a [[charge-coupled device]].  Scanning electron microscopes [[Raster scan|rasteri]] a finely focused electron beam, as in a TV set, across the studied sample to produce the image. Magnifications range from 100× to 1,000,000× or higher for both microscope types. The [[scanning tunneling microscope]] uses quantum tunneling of electrons from a sharp metal tip into the studied material and can produce atomically resolved images of its surface.<ref name="bozzola_1999">
{{cite book
 | last1 = Bozzola
 | first1 = J.J.
 | last2 = Russell
 | first2 = L.D.
 | title = Electron Microscopy: Principles and Techniques for Biologists
 | pages = 12, 197–199
 | publisher = [[Jones & Bartlett Learning|Jones & Bartlett Publishers]]
 | year = 1999
 | isbn = 978-0-7637-0192-5
 | url = https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA12
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084447/https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA12
 | url-status = live
}}</ref><ref>
{{cite book
 | last1 = Flegler | first1 = S.L.
 | last2 = Heckman | first2 = J.W. Jr.
 | last3 = Klomparens | first3 = K.L.
 | title = Scanning and Transmission Electron Microscopy: An Introduction
 |publisher=Oxford University Press |edition=Reprint |year=1995
 | pages = 43–45
 | isbn = 978-0-19-510751-7
}}</ref><ref>
{{cite book
 | last1 = Bozzola
 | first1 = J.J.
 | last2 = Russell
 | first2 = L.D.
 | title = Electron Microscopy: Principles and Techniques for Biologists
 | page = 9
 | publisher = [[Jones & Bartlett Learning|Jones & Bartlett Publishers]]
 | edition = 2nd
 | year = 1999
 | isbn = 978-0-7637-0192-5
 | url = https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA9
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204084444/https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA9
 | url-status = live
}}</ref>