Editing Electron microscope (section)

=== Transmission electron microscope (TEM) ===
{{Main|Transmission electron microscope}}
[[File:Electron_Microscope.png|right|frameless]]
The original form of the electron microscope, the [[transmission electron microscope]] (TEM), uses a [[high voltage]] [[electron beam]] to illuminate the specimen and create an image. An electron beam is produced by an [[electron gun]], with the electrons typically having energies in the range 20 to 400 keV, focused by [[Electromagnetism|electromagnetic]] lenses, and transmitted through the specimen. When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by lenses of the microscope. The spatial variation in this information (the "image") may be viewed by projecting the magnified electron image onto a [[Detectors for transmission electron microscopy|detector]]. For example, the image may be viewed directly by an operator using a fluorescent viewing screen coated with a [[phosphor]] or [[scintillator]] material such as [[zinc sulfide]]. A high-resolution phosphor may also be coupled by means of a lens optical system or a [[fibre optic]] light-guide to the sensor of a [[digital camera]]. [[Detectors for transmission electron microscopy#Direct electron detectors|Direct electron detectors]] have no scintillator and are directly exposed to the electron beam, which addresses some of the limitations of scintillator-coupled cameras.<ref>{{cite journal | vauthors = Cheng Y, Grigorieff N, Penczek PA, Walz T | title = A primer to single-particle cryo-electron microscopy | journal = Cell | volume = 161 | issue = 3 | pages = 438–449 | date = April 2015 | pmid = 25910204 | pmc = 4409659 | doi = 10.1016/j.cell.2015.03.050 }}</ref>

The resolution of TEMs is limited primarily by [[spherical aberration]], but a new generation of hardware correctors can reduce spherical aberration to increase the resolution in [[high-resolution transmission electron microscopy]] (HRTEM) to below 0.5 [[angstrom]] (50 [[picometre]]s),<ref name="Erni-2009">{{cite journal | vauthors = Erni R, Rossell MD, Kisielowski C, Dahmen U | title = Atomic-resolution imaging with a sub-50-pm electron probe | journal = Physical Review Letters | volume = 102 | issue = 9 | pages = 096101 | date = March 2009 | pmid = 19392535 | doi = 10.1103/PhysRevLett.102.096101 | bibcode = 2009PhRvL.102i6101E | osti = 960283 | url = https://www.escholarship.org/uc/item/3cs0m4vr }}</ref> enabling magnifications above 50 million times.<ref>{{cite web|url=http://www.sc.doe.gov/bes/scale_of_things.html |title=The Scale of Things |date=2006-05-26 |publisher=Office of Basic Energy Sciences, U.S. Department of Energy |access-date=2010-01-31 |url-status=dead |archive-url=https://web.archive.org/web/20100201175106/http://www.sc.doe.gov/bes/scale_of_things.html |archive-date=2010-02-01 }}</ref> The ability of HRTEM to determine the positions of atoms within materials is useful for nano-technologies research and development.<ref>{{cite web| vauthors = O'Keefe MA, Allard LF |title = Sub-Ångstrom Electron Microscopy for Sub-Ångstrom Nano-Metrology |url=http://www.osti.gov/bridge/servlets/purl/821768-E3YVgN/native/821768.pdf |publisher=Information Bridge: DOE Scientific and Technical Information – Sponsored by OSTI |date=2004-01-18}}</ref>