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1

Diffusion of Potassium on Nickel

100%

Błaszczyszynowa M., Błaszczyszyn R.

Acta Physica Polonica A

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1992

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vol. 81

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issue 2

285-294

EN

The surface diffusion of a potassium dose corresponding to the average coverage Θ̅_{K} = 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 migration with the energy Q < 0.16 eV is expected on the close-packed regions {111} and {001} already at liquid N_{2} temperature. The results are discussed in relation to the atomic structure of the nickel substrate taking into account the interaction in the adsorption layer.

2

Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip

81%

Błaszczyszyn R., Wachowicz E., Błaszczyszynowa M.

Acta Physica Polonica A

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1998

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vol. 93

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issue 5-6

763-773

EN

Interaction of hydrogen with vanadium layers preadsorbed on a thermally cleaned tungsten field emitter was studied at room temperature and 78 K through measurements of the total work function changes. An increase in the work function followed by its slight decrease at higher exposure can be understood taking into account the possibility of negatively (β^{-}) and positively (β^{+}) polarized adspecies formation on thin vanadium layer. This process leads to vanadium hydride formation. The work function results suggest that hydrogen diffusion into the vanadium layer is meaningful at room temperature. Thermal desorption of hydrogen adsorbate carried out within the temperature range 409-461 K from thin vanadium layer (Θ_{V} = 40) provided a value of 127 ± 6 kJ/mol for the activation energy for desorption.

3

Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel

81%

Błaszczyszyn R., Błaszczyszynowa M., Gubernator W.

Acta Physica Polonica A

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1995

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vol. 88

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issue 6

1151-1160

EN

Activation energy for thermal desorption of potassium from clean and sulfur covered surfaces of nickel was determined by means of the field emission method. For the low potassium coverage limit (Θ_{K} ≈ 0.02) the desorption was detected from the whole emitter surface in the temperature range of 825-1000 K for the atoms and of 725-825 K for the species of atoms and ions of the potassium. The activation energies of neutral desorption were found to be E^{a}_{Ni} = 3.8 eV for the clean nickel and E^{a}_{S/Ni} = 3.0 eV for the sulfur covered nickel, Θ_{s} ≈ 0.5. The activation energies for the desorption of the species of atoms and ions increased from E^{a+i}_{Ni} = 2.5 eV for the clean nickel to E^{a+i}_{S/Ni} = 2.9 eV for the sulfur covered nickel Θ_{s} ≈ 0.5. Also, a value of E^{a+i}_{S'/Ni} = 4.1 eV was found for a higher coverage of sulfur, Θ_{s} ≈ 1. The results are discussed in terms of Gurney model.

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Diffusion of Potassium on Nickel

Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip

Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel