THE CHANGE OF COVERAGE AND STRUCTURE OF THE SI(111)-ROOT-3-X-ROOT-3-AG SURFACE BY ISOTHERMAL ANNEALING

The thermal stability of the Si(111)-root 3 X root 3-Ag surface has be en studied by means of low energy electron diffraction, Auger electron spectroscopy, and Rutherford backscattering spectrometry techniques. The initial coverages of Ag, which was deposited on the Si(111)-7 X 7 surface at room temperature, are 0.8-1.0 ML (1 ML = 7.84 X 10(14) atom s/cm(2)). It is found that on isothermal annealing the coverage of Ag decreases exponentially with increasing time when only the root 3 X ro ot 3 spots continue to be observed and that the Ag coverage shifts to another slower exponential function at about 0.5 ML, at which the 3 X 1 spots begin to appear between the root 3 X root 3 spots. The activat ion energies for Ag atoms to decay from the Si(111)-root 3 X root 3-Ag and root 3 X root 3 + 3 X 1-Ag surfaces are determined from the two e xponential decay curves to be 0.89 +/- 0.21 and 2.6 +/- 0.3 eV, respec tively. The experimental values are compared with those obtained by ot her authors.