Editing Electron (section)

=== Confinement of individual electrons ===
Individual electrons can now be easily confined in ultra small ({{nowrap|1=''L'' = 20 nm}}, {{nowrap|1=''W'' = 20 nm}}) CMOS transistors operated at cryogenic temperature over a range of −269&nbsp;°C (4&nbsp;[[kelvin|K]]) to about −258&nbsp;°C (15&nbsp;[[kelvin|K]]).<ref>{{cite journal
 | last1 = Prati | first1 = E.
 | last2 = De Michielis | first2 = M.
 | last3 = Belli | first3 = M.
 | last4 = Cocco | first4 = S.
 | last5 = Fanciulli | first5 = M.
 | last6 = Kotekar-Patil | first6 = D.
 | last7 = Ruoff | first7 = M.
 | last8 = Kern | first8 = D.P.
 | last9 = Wharam | first9 = D.A.
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 | title = Few electron limit of n-type metal oxide semiconductor single electron transistors
 | journal = Nanotechnology
 | volume = 23 | issue = 21 | pages = 215204
 | year = 2012
 | doi = 10.1088/0957-4484/23/21/215204
 | pmid =  22552118 |arxiv = 1203.4811
 |bibcode = 2012Nanot..23u5204P | citeseerx = 10.1.1.756.4383 | s2cid = 206063658
 }}</ref> The electron wavefunction spreads in a semiconductor lattice and negligibly interacts with the valence band electrons, so it can be treated in the single particle formalism, by replacing its mass with the [[Effective mass (solid-state physics)|effective mass tensor]].