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Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel

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Błaszczyszyn R., Błaszczyszynowa M., Gubernator W.

Acta Physica Polonica A

1995

vol. 88

issue 6

1151-1160

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.

Investigation of Self-Diffusion of Titanium by Fluctuation Autocorrelation Method

100%

Dąbrowski A. M., Biernat T., Bęben J., Gubernator W.

Acta Physica Polonica A

1997

vol. 91

issue 6

1091-1095

Diffusion of titanium was examined in the field emission microscope using the fluctuation autocorrelation method. A thick titanium layer (about three monolayers) deposited on a tungsten tip was used. A temperature range of 1260-1410 K was found where diffusion can be described in a hydrodynamic approximation. In this temperature range the diffusion coefficient seems to comply with Arrhenius rule for the activation energy of 1.31 eV and D_{0} = 3×10^{-7} cm^{2}s.

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2 Acta Physica Polonica A

1 1997

1 1995

2 Gubernator W.

1 Biernat T.

1 Bęben J.

1 Błaszczyszyn R.

1 Błaszczyszynowa M.

1 Dąbrowski A. M.

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Thermal Desorption of Potassium from Clean and Sulfur Covered Nickel

Investigation of Self-Diffusion of Titanium by Fluctuation Autocorrelation Method