Editing Electron microscope (section)

== History ==
{{See also|Transmission electron microscopy#History}}
Many developments laid the groundwork of the [[electron optics]] used in microscopes.<ref name="Calbick-1944">{{Cite journal | vauthors = Calbick CJ |date=1944 |title=Historical Background of Electron Optics |journal=Journal of Applied Physics |volume=15 |issue=10 |pages=685–690 |doi=10.1063/1.1707371 |bibcode=1944JAP....15..685C }}</ref> One significant step was the work of [[Heinrich Hertz|Hertz]] in 1883<ref name="Hertz-2019">{{cite book | vauthors = Hertz H | veditors = Mulligan JF |chapter = Introduction to Heinrich Hertz's Miscellaneous Papers (1895) by Philipp Lenard |date=2019 | title = Heinrich Rudolf Hertz (1857-1894) : a collection of articles and addresses |pages=87–88 |publisher=Routledge |doi=10.4324/9780429198960-4 |isbn=978-0-429-19896-0 }}</ref> who made a cathode-ray tube with electrostatic and magnetic deflection, demonstrating manipulation of the direction of an electron beam. Others were focusing of the electrons by an axial magnetic field by [[Emil Wiechert]] in 1899,<ref name="Wiechert-1899">{{Cite journal | vauthors = Wiechert E |date=1899 |title=Experimentelle Untersuchungen über die Geschwindigkeit und die magnetische Ablenkbarkeit der Kathodenstrahlen |trans-title=Experimental Investigations on the Velocity and Magnetic Deflection of Cathode Rays |journal=Annalen der Physik und Chemie |language=de |volume=305 |issue=12 |pages=739–766 |doi=10.1002/andp.18993051203 |bibcode=1899AnP...305..739W }}</ref> improved oxide-coated cathodes which produced more electrons by [[Arthur Wehnelt]] in 1905<ref>{{Cite journal | vauthors = Wehnelt A |date=1905 |title=X. On the discharge of negative ions by glowing metallic oxides, and allied phenomena |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |volume=10 |issue=55 |pages=80–90 |doi=10.1080/14786440509463347 }}</ref> and the development of the electromagnetic lens in 1926 by [[Hans Busch]].<ref name="Busch-1926">{{Cite journal | vauthors = Busch H |date=1926 |title=Berechnung der Bahn von Kathodenstrahlen im axialsymmetrischen elektromagnetischen Felde |trans-title=Calculation of the trajectory of cathode rays in an axially symmetric electromagnetic field |journal=Annalen der Physik |language=de |volume=386 |issue=25 |pages=974–993 |doi=10.1002/andp.19263862507 |bibcode=1926AnP...386..974B }}</ref> According to [[Dennis Gabor]], the physicist [[Leo Szilard|Leó Szilárd]] tried in 1928 to convince him to build an electron microscope, for which Szilárd had filed a patent.<ref name="Dannen-1998">Dannen, Gene (1998)  [http://www.dannen.com/budatalk.html Leo Szilard the Inventor: A Slideshow (1998, Budapest, conference talk)]. dannen.com</ref>[[File:Ernst Ruska Electron Microscope - Deutsches Museum - Munich-edit.jpg|thumb|Reproduction of an early electron microscope constructed by [[Ernst Ruska]] in the 1930s]]To this day the issue of who invented the transmission electron microscope is controversial.<ref name="Mulvey-1962">{{Cite journal | vauthors = Mulvey T |date=1962 |title=Origins and historical development of the electron microscope |journal=British Journal of Applied Physics |volume=13 |issue=5 |pages=197–207 |doi=10.1088/0508-3443/13/5/303 }}</ref><ref name="Tao-2018">{{Cite book | vauthors = Tao Y |title=Proceedings of the 3rd International Conference on Contemporary Education, Social Sciences and Humanities (ICCESSH 2018) |chapter=A Historical Investigation of the Debates on the Invention and Invention Rights of Electron Microscope |date=2018 |chapter-url=https://www.atlantis-press.com/proceedings/iccessh-18/25898208 | series = Advances in Social Science, Education and Humanities Research |publisher=Atlantis Press |pages=1438–1441 |doi=10.2991/iccessh-18.2018.313 |isbn=978-94-6252-528-3}}</ref><ref name="Freundlich-1963">{{cite journal | vauthors = Freundlich MM | title = Origin of the Electron Microscope | journal = Science | volume = 142 | issue = 3589 | pages = 185–188 | date = October 1963 | pmid = 14057363 | doi = 10.1126/science.142.3589.185 | bibcode = 1963Sci...142..185F }}</ref><ref name="Rüdenberg-2010">{{cite book |doi=10.1016/s1076-5670(10)60005-5 |title=Origin and Background of the Invention of the Electron Microscope |series=Advances in Imaging and Electron Physics |date=2010 |volume=160 |pages=171–205 |isbn=978-0-12-381017-5 | vauthors = Rüdenberg R }}.</ref> In 1928, at the [[Technische Hochschule]] in Charlottenburg (now [[Technische Universität Berlin]]), Adolf Matthias (Professor of High Voltage Technology and Electrical Installations) appointed [[Max Knoll]] to lead a team of researchers to advance research on electron beams and cathode-ray oscilloscopes. The team consisted of several PhD students including [[Ernst Ruska]]. In 1931, [[Max Knoll]] and [[Ernst Ruska]]<ref name="Knoll-1932a">{{Cite journal | vauthors = Knoll M, Ruska E |date=1932 |title=Beitrag zur geometrischen Elektronenoptik. I |journal=Annalen der Physik |volume=404 |issue=5 |pages=607–640 |doi=10.1002/andp.19324040506 |bibcode=1932AnP...404..607K }}</ref><ref name="Knoll-1932b">{{Cite journal | vauthors = Knoll M, Ruska E |date=1932 |title=Das Elektronenmikroskop |journal=Zeitschrift für Physik |language=de |volume=78 |issue=5–6 |pages=318–339 |doi=10.1007/BF01342199 |bibcode=1932ZPhy...78..318K }}</ref> successfully generated magnified images of mesh grids placed over an anode aperture. The device, a replicate of which is shown in the figure, used two magnetic lenses to achieve higher magnifications, the first electron microscope. (Max Knoll died in 1969, so did not receive a share of the 1986 [[Nobel Prize|Nobel prize]] for the invention of electron microscopes.)

Apparently independent of this effort was work at [[Siemens-Schuckertwerke|Siemens-Schuckert]] by [[Reinhold Rudenberg|Reinhold Rüdenberg]]. According to patent law (U.S. Patent No. 2058914<ref name="Rüdenberg-1936">{{Cite web | vauthors = Rüdenberg R |title=Apparatus for producing images of objects |url=https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/2058914 |access-date=24 February 2023 |website=Patent Public Search Basic}}</ref> and 2070318,<ref>{{Cite web | vauthors = Rüdenberg R |title=Apparatus for producing images of objects |url=https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/2070318 |access-date=24 February 2023 |website=Patent Public Search Basic}}</ref> both filed in 1932), he is the inventor of the electron microscope, but it is not clear when he had a working instrument. He stated in a very brief article in 1932<ref name="Rodenberg-1932">{{cite journal |last1=Rüdenberg |first1=R. |title=Elektronenmikroskop |journal=Die Naturwissenschaften |date=July 1932 |volume=20 |issue=28 |pages=522 |doi=10.1007/BF01505383 |bibcode=1932NW.....20..522R }}</ref> that Siemens had been working on this for some years before the patents were filed in 1932, claiming that his effort was parallel to the university development. He died in 1961, so similar to Max Knoll, was not eligible for a share of the 1986 Nobel prize.<ref name="LEO Electron Microscopy">{{Cite web |title=History of Electron Microscope |url=https://www.leo-em.co.uk/history-of-electron-microscope.html |website=LEO Electron Microscopy |access-date=June 26, 2024}}</ref>

In the following year, 1933, Ruska and Knoll built the first electron microscope that exceeded the resolution of an optical (light) microscope.<ref name="Ruska, Ernst-1986">{{cite web |author=Ruska, Ernst |year=1986 |title=Ernst Ruska Autobiography |url=http://nobelprize.org/nobel_prizes/physics/laureates/1986/ruska-autobio.html |access-date=2010-01-31 |publisher=Nobel Foundation}}</ref>  Four years later, in 1937, Siemens financed the work of Ernst Ruska and [[Bodo von Borries]], and employed [[Helmut Ruska]], Ernst's brother, to develop applications for the microscope, especially with biological specimens.<ref name="Ruska, Ernst-1986" /><ref name="Kruger-2000">{{cite journal | vauthors = Kruger DH, Schneck P, Gelderblom HR | title = Helmut Ruska and the visualisation of viruses | journal = Lancet | volume = 355 | issue = 9216 | pages = 1713–1717 | date = May 2000 | pmid = 10905259 | doi = 10.1016/S0140-6736(00)02250-9 }}</ref> Also in 1937, [[Manfred von Ardenne]] pioneered the [[scanning electron microscope]].<ref>{{cite journal | vauthors = Von Ardenne M, Beischer D |title=Untersuchung von Metalloxyd-Rauchen mit dem Universal-Elektronenmikroskop |trans-title=Investigation of metal oxide smoking with the universal electron microscope |language=de |journal=Zeitschrift für Elektrochemie und Angewandte Physikalische Chemie |date=1940 |volume=46 |issue=4 |pages=270–277 |doi=10.1002/bbpc.19400460406 }}</ref> Siemens produced the first commercial electron microscope in 1938.<ref>[http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/materials/public/ElectronMicroscope/EM_HistOverview.htm History of electron microscopy, 1931–2000]. Authors.library.caltech.edu (2002-12-10). Retrieved on 2017-04-29.</ref> The first North American electron microscopes were constructed in the 1930s, at the [[Washington State University]] by Anderson and Fitzsimmons <ref>{{Cite web|url=https://news.wsu.edu/2018/05/14/wsu-home-north-americas-first-electron-microscope/|title = North America's first electron microscope}}</ref>  and at the [[University of Toronto]] by [[Eli Franklin Burton]] and students Cecil Hall, [[James Hillier]], and Albert Prebus. Siemens produced a transmission electron microscope (TEM) in 1939.<ref>{{cite web |url=http://web.mit.edu/Invent/iow/hillier.html |archive-url=https://web.archive.org/web/20030823110629/http://web.mit.edu/invent/iow/hillier.html |url-status=dead |archive-date=2003-08-23 |title=James Hillier|website=Inventor of the Week: Archive |date=2003-05-01 |access-date=2010-01-31}}</ref> Although current transmission electron microscopes are capable of two million times magnification, as scientific instruments they remain similar but with improved optics.

In the 1940s, high-resolution electron microscopes were developed, enabling greater magnification and resolution.<ref>{{cite book | vauthors = Hawkes PW |title=The Beginnings of Electron Microscopy. Part 1 |date=2021 |publisher=Academic Press |location=London San Diego, CA Cambridge, MA Oxford |isbn=978-0-323-91507-6}}</ref> By 1965, [[Albert Crewe]] at the [[University of Chicago]] introduced the scanning transmission electron microscope using a [[Field emission gun|field emission source]],<ref>{{Cite journal |last1=Crewe |first1=A. V. |last2=Eggenberger |first2=D. N. |last3=Wall |first3=J. |last4=Welter |first4=L. M. |date=1968-04-01 |title=Electron Gun Using a Field Emission Source |journal=Review of Scientific Instruments |volume=39 |issue=4 |pages=576–583 |doi=10.1063/1.1683435 |bibcode=1968RScI...39..576C }}</ref> enabling scanning microscopes at high resolution.<ref>{{cite journal | vauthors = Crewe AV | title = Scanning electron microscopes: is high resolution possible? | journal = Science | volume = 154 | issue = 3750 | pages = 729–738 | date = November 1966 | pmid = 17745977 | doi = 10.1126/science.154.3750.729 | bibcode = 1966Sci...154..729C }}</ref> By the early 1980s improvements in mechanical stability as well as the use of higher accelerating voltages enabled imaging of materials at the atomic scale.<ref>{{Cite journal |last1=Smith |first1=David J. |last2=Camps |first2=R. A. |last3=Freeman |first3=L. A. |last4=Hill |first4=R. |last5=Nixon |first5=W. C. |last6=Smith |first6=K. C. A. |date=May 1983 |title=Recent improvements to the Cambridge University 600 kV High Resolution Electron Microscope |journal=Journal of Microscopy |volume=130 |issue=2 |pages=127–136 |doi=10.1111/j.1365-2818.1983.tb04211.x }}</ref><ref name=":2">{{cite book |doi=10.1093/acprof:oso/9780199668632.001.0001 |title=High-Resolution Electron Microscopy |date=2013 |last1=Spence |first1=John C. H. |isbn=978-0-19-966863-2 }}{{page needed|date=January 2025}}</ref> In the 1980s, the [[field emission gun]] became common for electron microscopes, improving the image quality due to the additional coherence and lower chromatic aberrations. The 2000s were marked by advancements in aberration-corrected electron microscopy, allowing for significant improvements in resolution and clarity of images.<ref>{{cite journal |last1=Hawkes |first1=P. W. |title=Aberration correction past and present |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |date=28 September 2009 |volume=367 |issue=1903 |pages=3637–3664 |doi=10.1098/rsta.2009.0004 |pmid=19687058 |bibcode=2009RSPTA.367.3637H }}</ref><ref>{{cite journal |last1=Rose |first1=H. H. |title=Historical aspects of aberration correction |journal=Journal of Electron Microscopy |date=June 2009 |volume=58 |issue=3 |pages=77–85 |doi=10.1093/jmicro/dfp012 |pmid=19254915 }}</ref>