Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Field electron emission
(section)
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
=== Field electron emitters as electron-gun sources === [[File:Schottky-Emitter 01.jpg|thumb|Schottky-emitter electron source of an [[Electron microscope]]]] To achieve high-resolution in [[transmission electron microscope|electron microscopes]] and other electron beam instruments (such as those used for [[electron beam lithography]]), it is helpful to start with an electron source that is small, optically bright and stable. Sources based on the geometry of a Mueller emitter qualify well on the first two criteria. The first electron microscope (EM) observation of an individual atom was made by [[Albert Crewe]], J. Wall and J. Langmore in 1970,<ref name=CWL70>{{cite journal|doi=10.1126/science.168.3937.1338|title=Visibility of Single Atoms|year=1970|last1=Crewe|first1=A. V.|last2=Wall|first2=J.|last3=Langmore|first3=J.|journal=Science|volume=168|pages=1338β40|pmid=17731040|issue=3937|bibcode = 1970Sci...168.1338C |s2cid=31952480}}</ref> using a [[Scanning transmission electron microscopy|scanning transmission electron microscope]] equipped with an early field emission gun. From the 1950s onwards, extensive effort has been devoted to the development of field emission sources for use in [[electron gun]]s.<ref name=Ch95>{{cite journal|doi=10.1016/0169-4332(95)00517-X|title=Developing and using the field emitter as a high intensity electron source|year=1996|last1=Charbonnier|first1=F|journal=Applied Surface Science|volume=94-95|pages=26β43|bibcode = 1996ApSS...94...26C }}</ref><ref name=OR08>{{cite book|editor=J.Orloff|title=Handbook of Charged Particle Optics|edition=2|publisher=CRC Press|year=2008}}</ref><ref>L.W. Swanson and A.E. Bell, Adv. Electron. Electron Phys. 32 (1973) 193</ref> [e.g., DD53] Methods have been developed for generating on-axis beams, either by field-induced emitter build-up, or by selective deposition of a low-work-function [[adsorption|adsorbate]] (usually [[Zirconium oxide]] β ZrO) into the flat apex of a [[Miller index|(100) oriented]] [[Tungsten]] emitter.<ref name=Sw75>{{cite journal|doi=10.1116/1.568503|title=Comparative study of the zirconiated and built-up W thermal-field cathode|year=1975|last1=Swanson|first1=L. W.|journal=Journal of Vacuum Science and Technology|volume=12|page=1228|bibcode = 1975JVST...12.1228S|issue=6 }}</ref> Sources that operate at room temperature have the disadvantage that they can become covered with adsorbate [[molecule]]s that arrive from the [[vacuum]] system walls, and the emitter has to be cleaned from time to time by "flashing" to high temperature. Nowadays, it is common to use Mueller-emitter-based sources that are operated at elevated temperatures, either in the [[Thermionic emission|Schottky emission]] regime or in the so-called temperature-field intermediate regime. Most modern high-resolution electron microscopes and electron beam instruments use some form of field emission electron source. Currently, attempts are being made to develop [[carbon nanotubes]] (CNTs) as electron-gun field emission sources.<ref name=Milne/><ref name=JB04>{{cite journal|doi=10.1098/rsta.2004.1438|title=Carbon nanotube electron sources and applications|year=2004|last1=De Jonge|first1=Niels|last2=Bonard|first2=Jean-Marc|journal=Philosophical Transactions of the Royal Society A|volume=362|pages=2239β66|pmid=15370480|issue=1823|bibcode = 2004RSPTA.362.2239D |s2cid=14497829}}</ref> The use of field emission sources in electron optical instruments has involved the development of appropriate theories of charged particle optics,<ref name=OR08/><ref name=HK96>{{cite book|author1=P.W. Hawkes |author2=E. Kaspar |title=Principles of Electron Optics|publisher=Academic Press, London|year= 1996|chapter=44,45|volume=2}}</ref> and the development of related modeling. Various shape models have been tried for Mueller emitters; the best seems to be the "Sphere on Orthogonal Cone" (SOC) model introduced by Dyke, Trolan. Dolan and Barnes in 1953.<ref name=DTDB53>{{cite journal|doi=10.1063/1.1721330|title=The Field Emitter: Fabrication, Electron Microscopy, and Electric Field Calculations|year=1953|last1=Dyke|first1=W. P.|last2=Trolan|first2=J. K.|last3=Dolan|first3=W. W.|last4=Barnes|first4=George|journal=Journal of Applied Physics|volume=24|page=570|bibcode = 1953JAP....24..570D|issue=5 }}</ref> Important simulations, involving trajectory tracing using the SOC emitter model, were made by Wiesener and Everhart.<ref name=Ev67>{{cite journal|doi=10.1063/1.1709260|title=Simplified Analysis of Point-Cathode Electron Sources|year=1967|last1=Everhart|first1=T. E.|journal=Journal of Applied Physics|volume=38|page=4944|bibcode = 1967JAP....38.4944E|issue=13 }}</ref><ref>{{cite journal|doi=10.1063/1.1662526|title=Point-cathode electron sources-electron optics of the initial diode region|year=1973|last1=Wiesner|first1=J. C.|journal=Journal of Applied Physics|volume=44|page=2140|bibcode = 1973JAP....44.2140W|issue=5 |doi-access=free}}</ref><ref>{{cite journal|doi=10.1063/1.1663676|title=Point-cathode electron sources-Electron optics of the initial diode region: Errata and addendum|year=1974|last1=Wiesner|first1=J. C.|journal=Journal of Applied Physics|volume=45|page=2797|bibcode = 1974JAP....45.2797W|issue=6 |doi-access=free}}</ref> Nowadays, the facility to simulate field emission from Mueller emitters is often incorporated into the commercial electron-optics programmes used to design electron beam instruments. The design of efficient modern field-emission electron guns requires highly specialized expertise.
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)