BINDING AND MOBILITY OF ISOLATED INDIUM ATOMS ON SI(111)7X7

PAC spectroscopy has been used to study diffusion and desorption of isolated In-111 atoms adsorbed on a Si(111)7 x 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 be 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 be 1.93(10) eV. The desorption behavior is found to be strongly dependent on In concentration in the low coverage regime.