Joel M. Vaughn

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Model scandate thermionic cathodes have been prepared by rf reactive sputtering of scandium oxide and barium oxide onto tungsten foil. By preparing separate, 200 nm thick layers of these oxides, sputtered through different sized masks, the function of barium oxide and scandium oxide can be identified directly in the thermionic electron emission image.(More)
Introduction Thermionic cathodes are used in many industrial vacuum electronic applications. Vacuum tubes for high-frequency or high-power applications are one example (e.g., see [1]). The emission properties of thermionic electron sources in vacuum devices are often Bimproved[ by the addition of oxide coatings on the metal cathode surface [2, 3]. The(More)
Many theories [1] of work function reduction on scandate cathodes rely on a monolayer surface dipole layer of Ba-Sc-O-W. The charge transfer between the surface atoms, in particular the electron transfer from the barium ion, is the primary agent of work function reduction. We have examined thick (200 nm) layers of reactively sputtered(More)
Thin film model cathodes prepared as 200nm nominally thick sputter deposited coatings in many configurations of Sc, Sc<inf>2</inf>O<inf>3</inf>, Ba, BaO on W foil (0.05mm thick) were studied using photoelectron emission microcopy (PEEM) and thermionic emission microscopy (ThEEM) in a Bauer-Telieps style LEEM/PEEM. The sample structures are shown(More)
The transport of Ba to the surface of a porous tungsten disk packed with barium oxide powder is observed directly with emission microscopy. The W disk surface is patterned with sputter deposited scandium metal squares. Thermionic electron emission is observed from the Ba/Sc/W areas at temperatures below those required for thermionic electron emission from(More)
Thermionic electron emission from 200 to 500 nm thick coatings of scandium oxide on tungsten foil have been examined in thermionic emission microscopy, spectroscopic photoelectron microcopy, synchrotron radiation and ultraviolet photoelectron spectroscopy (UPS). A clear dependence of the scandium oxide-W electron yield on the grain orientation of the(More)
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