Measurement of step and kink energies and of the step-edge stiffness from island studies on Pt(111)

By using temperature-variable scanning tunneling microscopy, we studied two-dimensional vacancy islands on Pt(111) between 593 and 713 K. Due to the difference in the step free energies of A and B steps, the equilibrium shape of the vacancy islands has a threefold symmetry. From the analysis of the equilibrium shape of the vacancy islands, we calculate the angular dependence of the step free energy on Pt(111). The absolute values for the step free energies per atom of A and B steps are determined from the equilibrium shape fluctuations to be beta(A)=348 +/- 16 meV/atom and beta(B)=300 +/- 14 meV/atom, respectively. Furthermore, we derive the temperature dependence of the step-edge stiffness (beta) over tilde with (beta) over tilde (A) between 510 and 453 meV/atom and (beta) over tilde (B) between 1974 and 1104 meV/atom in the temperature range considered. From the stiffness, we obtain the kink formation energies for A and B steps, epsilon(A)=143 +/- 9 meV and epsilon(B)=206 +/- 9 meV, respectively.