Diffusion of Potassium on Nickel

Abstract

The surface diffusion of a potassium dose corresponding to the average coverage ΘK = 1.5 on nickel was studied using the field emission technique in the temperature range of 78-133 K. In general, under such conditions diffusion proceeds with the sharp moving boundary and the activation energy Q from 0.16 eV to 0.36 eV dependently on the crystallographic directions. Free boundary migoation with the energy Q < 0.16 eV is expected on the close-packed regions {111) and {001) already at liquid Ν2 temperature. The results are discussed in relation to the atomic structure of the nickel substrate taking into account the interaction in the adsorption layer.

Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel

“…This effect generally is the result of the relatively high work function φ of some single planes of nickel, particularly {111} and {100} (from 5.2 to 5.56 eV and 5.1 to 5.22 eV, respectively [15]) with respect to the ionization potential of potassium I = 4.34 eV. At the beginning of the adsorption the adsorbate could be accumulated on these planes under the diffusion equilibrium conditions [2,16]. In the rough approximation the results are in agreement with the relation The obtained value of Εa+iNi = 2.5 eV is close to other results concerning the activation energy for desorption of potassium, e.g.…”