Growth of Ag on MgO(0 0 1) studied in situ by grazing incidence small angle X-ray scattering

The morphology of growing Ag nanoparticles on MgO(0 0 1) surfaces was investigated in situ, from the very beginning of the deposit up to the later stages (several nanometers), by grazing incidence small angle X-ray scattering (GISAXS), at different substrate temperatures (T = 300, 540 and 640 K). At the end of the deposit, the two samples elaborated at 300 and 540 K were also studied by transmission electron microscopy (TEM). The GISAXS patterns give evidence of a process of nucleation, growth and finally coalescence of islands. From the GISAXS data, the evolution of the inter-island distance, the lateral size, the height of the islands as well as their size distribution are derived as a function of the Ag deposited thickness and of the temperature. A very good agreement is obtained between the dimensional parameters found by TEM and GISAXS. Above 640 K, the islands adopt their equilibrium shape of truncated octahedron and the metal/oxide adhesion energy can be deduced.