Hundred years anniversary of the oxide cathode—A historical review Georg Gaertner a, * , Daniel den Engelsen b a Philips Research Laboratories, Weisshausstrasse 2, D-52066 Aachen, Germany b LG. Philips Displays Netherlands, P.O. Box 807, 5600 AV Eindhoven, The Netherlands Available online 13 June 2005 Abstract In this year, we celebrate the 100 years anniversary of Arthur Wehnelts discovery of the oxide cathode. In his famous article in ‘‘Annalen der Physik’’ in 1904 Wehnelt showed that coating of noble metals with alkaline earth oxides, such as BaO and CaO lowered cathode fall and work function drastically. This was the start of the oxide cathode, which has become one of the most commonly used electron sources in vacuum tube technology and also in low pressure gas discharge lamps. In the past century, a vast amount of literature has been generated on the technology and emission mechanisms of the oxide cathode. This paper reviews the evolution of technology, applications and theoretical models of the oxide cathode from 1904 to the present status. # 2005 Elsevier B.V. All rights reserved. PACS: 79.40 Keywords: Oxide cathode; Arthur Wehnelt; Thermionic emission; Vacuum tube 1. Introduction Now 100 years have passed, since Arthur Wehnelt (see Fig. 1) published his famous paper entitled: ‘‘U ¨ ber den Austritt negativer Ionen aus glu ¨henden Metallverbindungen und damit zusammenha ¨ngende Erscheinungen’’ [1a]. Literally translated from Ger- man it means: ‘‘On the emission of negative ions from glowing metal compounds and related phenomena’’. This paper was the start of the oxide cathode, which has become the work horse not only in cathode ray tubes with a production of about 700 million oxide cathodes in 2000, but also in low pressure gas discharge lamps with about seven billion pieces produced in the same year. It should be mentioned that Arthur Wehnelt had already published a preliminary report on his activities in 1903 [1b]. 2. Arthur Wehnelt and his epochal publication Arthur Rudolph Berthold Wehnelt was a German physicist, who was born in Rio de Janeiro on 4.4.1871 www.elsevier.com/locate/apsusc Applied Surface Science 251 (2005) 24–30 * Corresponding author. Tel.: +49 241 6003 337; fax: +49 241 6003 465. E-mail address: georg.gaertner@philips.com (G. Gaertner). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.03.214