The perturbed γγ angular correlation method has been used to study diffusion and desorption of isolated ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ atoms adsorbed on a Si(111)7×7 surface. Two different adsorption sites are found and their hyperfine parameters are determined as a function of temperature and compared to first-principles calculations. The activation energy for the migration to regular adsorption sites is determined to 0.72(5) eV. The relative population of the two adsorption sites changes at about 500 K corresponding to an activation energy of 1.61(15) eV for this process. The binding energy of the indium atoms is estimated to 1.93(10) eV. The desorption behavior is found to be strongly dependent on In concentration in the low coverage regime.

• Received 1 October 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.377