Nucleation and growth of supported clusters at defect sites: Pd/MgO(001)

Nucleation and growth of Pd on cleaved MgO(001) surfaces were studied by va riable-temperature atomic force microscopy in the temperature range 200-800 K. Constant island densities (similar to 3x10(12)cm(-2)) were observed ove r a wide temperature range, indicating nucleation kinetics governed by poin t defects with a high trapping energy. These results are compared to a rate equation model that describes the principal atomistic nucleation and growt h processes, including nucleation at attractive point defects. Energies for defect trapping, adsorption, surface diffusion, and pair binding are deduc ed, and compared with recent nb initio calculations.