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Interaction and diffusion of potassium on Cr2O3,,0001...Cr,,110... W. Zhao, G. Kerner, and M. Asscher*

Summary: Interaction and diffusion of potassium on Cr2O3,,0001...ŐCr,,110...
W. Zhao, G. Kerner, and M. Asscher*
Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel
X. M. Wilde, K. Al-Shamery, and H.-J. Freund
The Fritz Haber Institute der Max-Planck Gesellschaft, Faradayweg 4-6, Berlin, Germany
V. Staemmler and M. Wieszbowska
Universitašt fušr Theoretical Chemie, Ruhr Universitašt Bochum, D-44780, Germany
Received 24 March 1999; revised manuscript received 9 February 2000
The interaction of potassium atoms on top of Cr2O3 0001 /Cr 110 has been studied using work-function
, temperature programmed desorption TPD , and optical second-harmonic generation SHG measure-
ments. Potassium grows via the completion of a first layer, followed by a second layer in the form of
two-dimensional 2D islands, and at higher coverage 3D clusters are formed. This growth model is supported
by and consistent with the results obtained from all three methods. Work-function data suggest that annealing
at temperatures above 350 K results in the formation of a surface potassium oxide compound, provided the
potassium coverage is higher than 0.5 monolayers ML . Diffusion of alkali-metal atoms on an oxide surface
is reported here over distances of several micrometers. This was measured using optical SH diffraction from
coverage gratings that were generated by laser-induced thermal desorption. The activation energy for surface
diffusion of potassium on Cr2O3 0001 /Cr 110 has been determined to be 11 0.5 kcal/mol with a preexpo-
nential factor D0 105


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry