Electron-stimulated cesium atom desorption from the Cs/CsAu/Au/W system |
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Authors: | V N Ageev Yu A Kuznetsov and N D Potekhina |
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Institution: | 1.Ioffe Physical-Technical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021, Russia ; |
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Abstract: | This paper reports on a continuation of the investigation of electron-stimulated Cs-atom desorption from a tungsten surface
on which cesium and gold films had been adsorbed at T = 300 K. Earlier studies revealed that Cs atoms start to desorb only after more than one monolayer of gold and more than
one monolayer of cesium had been deposited on the tungsten surface. In this case, a coating consisting of a gold adlayer on
tungsten, a CsAu compound possessing semiconducting properties, and a cesium monolayer capping CsAu (Cs/CsAu/Au/W) is formed
on the tungsten surface at 300 K. The yield of atoms from this system exhibits a resonant dependence on the incident electron
energy E
e
, with an appearance threshold of 57 eV and a maximum at 64 eV. In this case, Cs atoms desorb in two channels, with one of
them involving Cs desorption out of the cesium monolayer, and the other, from the CsAu monolayer. The Cs yield at E
e
= 64 eV has been investigated in both desorption channels, with an additional cesium coating deposited on the already formed
Cs/CsAu/Au/W layered system, as well as of the effect annealing produces on the yield and energy distributions of Cs atoms.
It has been demonstrated that Cs atoms evaporated at 300 K on a layered coating with a cesium monolayer atop the CsAu layer
on tungsten capped with a gold adlayer, rather than reflected from the cesium monolayer or adsorbing on it, penetrate through
the cesium monolayer into the bulk of CsAu even with one CsAu layer present. The desorption yield does not vary with increasing
cesium concentration at 300 K, but falls off gradually at 160 K. Annealing within the temperature range 320 K ≤ T
H
≤ 400 K destroys the cesium monolayer and the one-layer CsAu coating, but the multilayer CsAu compound does not break up
in this temperature range even after evaporation of the cesium monolayer. It is shown that Cs atoms escape from the multilayer
CsAu compound primarily out of the top CsAu layer. |
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