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| {{Infobox scientist
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| |name = Walter H. Schottky
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| |image = Walter Hermann Schottky (1886-1976).jpg
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| |birth_date = {{birth-date|23 July 1886|23 July 1886}}
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| |birth_place = [[Zürich]], [[Switzerland]]
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| |death_date = {{death-date|4 March 1976|4 March 1976}}
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| |death_place = [[Pretzfeld]], [[West Germany]]
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| |residence = Germany
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| |citizenship =
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| |nationality = German
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| |ethnicity =
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| |fields = [[Physicist]]
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| |workplaces = [[University of Jena]]<br />[[University of Würzburg]]<br />[[University of Rostock]]<br />[[Siemens AG|Siemens Research Laboratories]]
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| |alma_mater = [[University of Berlin]]
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| |doctoral_advisor = [[Max Planck]]<br />[[Heinrich Rubens]]
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| |academic_advisors =
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| |doctoral_students =
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| |notable_students = [[Werner Hartmann (physicist)|Werner Hartmann]]
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| |known_for = [[Schottky effect]]<br />[[Schottky barrier]]<br />[[Schottky contact]]<br />[[Schottky anomaly]]<br />[[Screen-grid|Screen-grid vacuum tube]]<br />[[Tetrode]]<br />[[Ribbon microphone]]<br />[[Loudspeaker#Ribbon_and_planar_magnetic_loudspeakers|Ribbon loudspeaker]]<br />[[Field electron emission|Theory of Field emission]]<br />[[Shot noise]]
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| |influences =
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| |influenced =
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| |awards = [[Hughes medal]] (1936)<br />[[Werner von Siemens Ring]] (1964)
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| |religion =
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| |signature = <!--(filename only)-->
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| |footnotes = His father was the [[mathematician]] [[Friedrich Hermann Schottky]].
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| }}
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| '''Walter Hermann Schottky''' (23 July 1886, [[Zürich]], Switzerland – 4 March 1976, [[Pretzfeld]], West Germany) was a German physicist who played a major early role in developing the theory of electron and ion emission phenomena, invented the [[Screen-grid#Screen grid|screen-grid]] [[vacuum tube]] in 1915 and the [[pentode]]{{Citation needed|date=March 2011}} in 1919 while working at [[Siemens AG|Siemens]], co-invented the [[Ribbon microphone]] and [[Loudspeaker#Ribbon_and_planar_magnetic_loudspeakers|Ribbon Loudspeaker]] along with Dr. Gerwin Erlach in 1924<ref name="Ribbon">{{Cite news|url=http://www.hi-fiworld.co.uk/loudspeakers/66-knowledge/152-historically-speaking-part-ii.html|title=Historically Speaking|publisher=Hifi World|date=April 2008|accessdate=April 2012}}</ref> and later made many significant contributions in the areas of semiconductor devices, technical physics and technology. | |
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| ==Education==
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| He graduated from the [[Steglitz Gymnasium]], Berlin, Germany in 1904. He obtained his BS in [[Physics]], at the [[University of Berlin]] in 1908. He obtained his PhD in Physics at the [[University of Berlin]] in 1912 under [[Max Planck]] and [[Heinrich Rubens]], with a thesis entitled: ''Zur relativtheoretischen Energetik und Dynamik''.
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| ==Career==
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| His postdoctoral period was spent at [[University of Jena]] (1912–14). He then lectured at the [[University of Würzburg]] (1919–23). He became Professor of Theoretical Physics, [[University of Rostock]] (1923–27). For two periods he worked at the Siemens Research laboratories (1914–19, 1927–58).
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| ==Inventions==
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| In 1924, Schottky co-invented the [[Ribbon microphone]] along with Dr. Gerwin Erlach. The idea was that a very fine ribbon suspended in a magnetic field could generate electric signals. This in turn lead also to the invention of the [[Loudspeaker#Ribbon_and_planar_magnetic_loudspeakers|Ribbon Loudspeaker]] by using it in the reverse order, but not until high flux permanent magnets became available in the late 1930s.<ref name="Ribbon"></ref>
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| ==Major scientific achievements==
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| Possibly, in retrospect, Schottky's most important scientific achievement was to develop (in 1914) the well-known classical formula, now written -''q''<sup>2</sup>/16π''ε''<sub>0</sub>''x'', for the interaction energy between a point [[electric charge|charge]] ''q'' and a ''flat'' metal surface, when the charge is at a distance ''x'' from the surface. Owing to the method of its derivation, this interaction is called the "image potential energy" (image PE). Schottky based his work on earlier work by [[William Thomson, 1st Baron Kelvin|Lord Kelvin]] relating to the image PE for a sphere. Schottky's image PE has become a standard component in simple models of the barrier to motion, ''M''(''x''), experienced by an electron on approaching a metal surface or a metal–[[semiconductor]] interface from the inside. (This ''M''(''x'') is the quantity that appears when the one-dimensional, one-particle, [[Schrödinger equation]] is written in the form
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| :<math>\frac{d^2}{dx^2} \Psi(x) = \frac{2m}{\hbar^2} M(x) \Psi(x) .</math> | | '''source''' |
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| Here, <math> \hbar </math> is [[Planck's constant]] divided by 2π, and ''m'' is the [[electron mass]].)
| | <span style="color: red">Follow this [https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering link] to change your Math rendering settings.</span> You can also add a [https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering-skin Custom CSS] to force the MathML/SVG rendering or select different font families. See [https://www.mediawiki.org/wiki/Extension:Math#CSS_for_the_MathML_with_SVG_fallback_mode these examples]. |
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| The image PE is usually combined with terms relating to an applied [[electric field]] ''F'' and to the height ''h'' (in the absence of any field) of the barrier. This leads to the following expression for the dependence of the barrier energy on distance ''x'', measured from the "electrical surface" of the metal, into the [[vacuum]] or into the [[semiconductor]]:
| | ==Demos== |
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| :<math> M(x) = \; h -eFx - e^2/4 \pi \epsilon_0 \epsilon_r x \;. </math> | | Here are some [https://commons.wikimedia.org/w/index.php?title=Special:ListFiles/Frederic.wang demos]: |
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| Here, ''e'' is the [[elementary charge|elementary positive charge]], ''ε''<sub>0</sub> is the [[electric constant]] and ''ε''<sub>r</sub> is the [[relative permittivity]] of the second medium (=1 for [[vacuum]]). In the case of a [[metal–semiconductor junction]], this is called a [[Schottky barrier]]; in the case of the metal-vacuum interface, this is sometimes called a [[Field electron emission|Schottky–Nordheim barrier]]. In many contexts, ''h'' has to be taken equal to the local [[work function]] ''φ''.
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| This [[Field electron emission|Schottky–Nordheim barrier]] (SN barrier) has played in important role in the theories of [[thermionic emission]] and of [[field electron emission]]. Applying the field causes lowering of the barrier, and thus enhances the emission current in [[thermionic emission]]. This is called the "[[Thermionic emission|Schottky effect]]", and the resulting emission regime is called "[[Thermionic emission|Schottky emission]]".
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| | ** Orca: There is ongoing work, but no support at all at the moment [[File:Orca-mathml-example-1.wav|thumb|Orca-mathml-example-1]], [[File:Orca-mathml-example-2.wav|thumb|Orca-mathml-example-2]], [[File:Orca-mathml-example-3.wav|thumb|Orca-mathml-example-3]], [[File:Orca-mathml-example-4.wav|thumb|Orca-mathml-example-4]], [[File:Orca-mathml-example-5.wav|thumb|Orca-mathml-example-5]], [[File:Orca-mathml-example-6.wav|thumb|Orca-mathml-example-6]], [[File:Orca-mathml-example-7.wav|thumb|Orca-mathml-example-7]]. |
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| In 1923 Schottky suggested (incorrectly) that the experimental phenomenon then called autoelectronic emission and now called [[field electron emission]] resulted when the barrier was pulled down to zero. In fact, the effect is due to [[quantum tunnelling|wave-mechanical tunneling]], as shown by Fowler and Nordheim in 1928. But the [[Field electron emission|SN barrier]] has now become the standard model for the tunneling barrier.
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| Later, in the context of [[semiconductor devices]], it was suggested that a similar barrier should exist at the junction of a metal and a semiconductor. Such barriers are now widely known as [[Schottky barrier]]s, and considerations apply to the transfer of electrons across them that are analogous to the older considerations of how electrons are emitted from a metal into vacuum. (Basically, several emission regimes exist, for different combinations of field and temperature. The different regimes are governed by different approximate formulae.)
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| When the whole behaviour of such interfaces is examined, it is found that they can act (asymmetrically) as a special form of electronic diode, now called a [[Schottky diode]]. In this context, the metal–semiconductor junction is known as a "[[Schottky contact|Schottky (rectifying) contact']]".
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| Schottky's contributions, in surface science/emission electronics and in semiconductor-device theory, now form a significant and pervasive part of the background to these subjects. It could possibly be argued that – perhaps because they are in the area of technical physics – they are not as generally well recognized as they ought to be.
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| ==Awards==
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| He was awarded the [[Royal Society]]'s [[Hughes medal]] in 1936 for his discovery of the [[Schrot effect]] (spontaneous current variations in high-vacuum discharge tubes, called by him the "Schrot effect": literally, the "small shot effect") in [[thermionic emission]] and his invention of the screen-grid tetrode and a [[superheterodyne]] method of receiving wireless signals.
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| In 1964 he received the [[Werner von Siemens Ring]] honoring his ground-breaking work on the physical understanding of many phenomena that led to many important technical appliances, among them [[tube amplifier]]s and [[semiconductor]]s.
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| ==Controversy==
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| The invention of superheterodyne is usually attributed to [[Edwin Armstrong]]. However, Schottky published an article in [[Proc. IRE]] that he had also invented something similar.
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| * 1939: first [[p-n junction]] | |
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| ==Personal life==
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| His father was [[mathematician]] [[Friedrich Hermann Schottky]] (1851–1935). His wife was Elizabeth and they had one daughter and two sons. His father was appointed professor of mathematics at the [[University of Zurich]] in 1882, and he was born 4 years later. The family then moved back to Germany in 1892, where his father took up an appointment at the [[University of Marburg]].
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| ==Legacy==
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| [[:de:Walter Schottky Institut|Walter Schottky Institute]] (Germany) was named after him. The [[:de:Walter-Schottky-Preis|Walter H. Schottky prize]] is named after him.
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| ==Books written by Schottky== | |
| * ''Thermodynamik'', Julius Springer, Berlin, Germany, 1929.
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| * ''Physik der Glühelektroden'', Akademische Verlagsgesellschaft, Leipzig, 1928.
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| ==See also==
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| * [[Schottky defect]]
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| ==References==
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| {{Reflist}}
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| ==External links==
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| * [http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_2/advanced/t2_1_3.html Walter Schottky]
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| * [http://www.webcitation.org/query?url=http://www.geocities.com/bioelectrochemistry/schottky.htm&date=2009-10-25+19:12:49 Biography of Walter H. Schottky]
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| * [http://www.wsi.tum.de/ Walter Schottky Institut]
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| * {{DNB portal|118759183|TYP=}}
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| * [http://www.gnt-verlag.de/de/?id=88 Reinhard W. Serchinger: Walter Schottky – Atomtheoretiker und Elektrotechniker.] Sein Leben und Werk bis ins Jahr 1941. Diepholz; Stuttgart; Berlin: GNT-Verlag, 2008.
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| * [http://www.nndb.com/people/438/000172919/ Schottky's nndb profile]
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| * [http://genealogy.math.ndsu.nodak.edu/id.php?id=55830 Schottky's math genealogy]
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| {{Use dmy dates|date=December 2010}}
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| {{Persondata <!-- Metadata: see [[Wikipedia:Persondata]]. -->
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| | NAME = Schottky, Walter H.
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| | ALTERNATIVE NAMES =
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| | SHORT DESCRIPTION =
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| | DATE OF BIRTH = 23 July 1886
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| | PLACE OF BIRTH = [[Zürich]], [[Switzerland]]
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| | DATE OF DEATH = 4 March 1976
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| | PLACE OF DEATH = [[Pretzfeld]], [[West Germany]]
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| }}
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| {{DEFAULTSORT:Schottky, Walter H.}}
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| [[Category:Semiconductor physicists]]
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| [[Category:1886 births]]
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| [[Category:1976 deaths]]
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| [[Category:German electrical engineers]]
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| [[Category:German physicists]]
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| [[Category:Werner von Siemens Ring laureates]]
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| [[be-x-old:Вальтэр Шоткі]]
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| [[ca:Walter H. Schottky]]
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| [[cs:Walter Schottky]]
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| [[de:Walter Schottky]]
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| [[et:Walter Schottky]]
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| [[es:Walter H. Schottky]]
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| [[fr:Walter Schottky]]
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| [[id:Walter H. Schottky]]
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| [[it:Walter Schottky]]
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| [[lt:Walter Schottky]]
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| [[mr:वॉल्टर शॉट्की]]
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| [[nl:Walter Schottky]]
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| [[ja:ヴァルター・ショットキー]]
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| [[pl:Walter Schottky]]
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| [[pt:Walter Schottky]]
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| [[ro:Walter Schottky]]
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| [[ru:Шоттки, Вальтер]]
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| [[uk:Вальтер Шотткі]]
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| [[zh:華特·蕭特基]]
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