Search results

1

Reflection Electron Energy Loss Spectroscopy of Alkali Metals on Silicon

100%

Kleint C., Abd El-Halim S.

Acta Physica Polonica A

|

1992

|

vol. 81

|

issue 1

47-65

EN

In an extended introduction studies of alkali adsorption on clean silicon surfaces are shortly reviewed and recent achievements are outlined. The main part describes our investigations of lithium and potassium adsorption by reflection electron energy loss spectroscopy (REELS). Beside (electronic) valence electron excitations also core losses of both silicon and these alkali metals were observed in the ionization loss spectroscopy mode (ILS). Additional information has been obtained by Auger electron spectroscopy (AES) and measurements of work function changes (WFC). The spectra of Li and K adsorption on the Si(100) plane show considerable differences which will be discussed in detail. By simulation of the REEL potassium spectra within the density of states (DOS) model using the Si(100)2 × 1 K DOS by R. Ramirez the origin of the 8.4 and 12.5 eV loss peaks can be traced to band structure features. In addition the known K peaks at 18.1, 20 and 22 eV are confirmed and their behaviour with increasing primary energy E_{p}, was investigated. While the K 3p-K 4s transition corresponding to the 18.1 eV loss increases with E_{p}, the dipole-forbidden K 3p-K 4p transition (20 eV) decreases. Shifts in the loss energy of these peaks as well as in the core loss energies at 295 and 296.8 eV are observed and explained by charge transfer.

2

Temperature Dependence of the Preexponential Factors of the Field Emission Flicker Noise Cross-Correlation Function for W(110)K

100%

Dąbrowski A., Kleint C.

Acta Physica Polonica A

|

1992

|

vol. 81

|

issue 4-5

583-588

EN

In a field emission tube with two probe-holes the cross-correlation functions of current fluctuations from potassium submonolayers on tungsten have been investigated. The measurements were carried out in the temperature range of 290-430 K and with coverages between 0.05 and 0.87. The experimental correlation curves were approximated by a sum of three exponential functions revealing three components with different time constants τ_{i} and amplitudes R. The temperature dependence of the amplitudes R_{2} and R_{3} is discussed in terms of collective flip-flop processes.

3

Diffusion of Potassium on the W(112) Plane Preadsorbed by Ni Atoms: Field Emission Current Fluctuations - Autocorrelation Study

81%

Biernat T., Błaszczyszyn R., Kleint C.

Acta Physica Polonica A

|

2001

|

vol. 99

|

issue 6

665-672

EN

Diffusion of potassium adsorbate on the W(112) plane with preadsorbed nickel was investigated by means of the autocorrelation function of field emission current fluctuations. A comparison of the experimental autocorrelation function with that of a theoretical calculation by Gesley and Swanson gives the surface diffusion coefficient of potassium. From its temperature dependence the diffusion activation energy at several Ni pre-coverages for a constant potassium coverage (Θ_K=0.4) is derived. The dependence of the activation energy for potassium surface diffusion on the nickel coverage - first reduction and then an increase with increasing Ni coverage - is observed. This is in agreement with the results obtained from the spectral analysis of the field emission current fluctuations of the same system. The decrease is understood to be a result of the smoothing effect caused by Ni atoms on the W(112) plane.

Refine search results

3 Acta Physica Polonica A

1 2001

2 1992

3 Kleint C.

1 Abd El-Halim S.

1 Biernat T.

1 Błaszczyszyn R.

1 Dąbrowski A.

Reflection Electron Energy Loss Spectroscopy of Alkali Metals on Silicon

Temperature Dependence of the Preexponential Factors of the Field Emission Flicker Noise Cross-Correlation Function for W(110)K

Diffusion of Potassium on the W(112) Plane Preadsorbed by Ni Atoms: Field Emission Current Fluctuations - Autocorrelation Study