Adhesion of growing nanoparticles at a glance: Surface differential reflectivity spectroscopy and grazing incidence small angle x-ray scattering

This paper compares the capability of surface differential reflectivity spectroscopy (SDRS) and grazing incidence small angle x-ray scattering (GISAXS) to characterize in situ, "at a glance," a collection of nanoclusters by statistically defining the geometry of an average particle (diameter, height, and interparticle distance). SDRS and GISAXS are run simultaneously on Ag/MgO(001) films during their growth. They are shown to lead to consistent values of the morphological parameters, with a particular good agreement about the aspect ratio (height/diameter) which, thanks to the basic physics underlying the two measurements, is determined in both cases. By modeling silver particles by truncated spheres, close estimates of the wetting angle and of the adhesion energy are derived (0.75 +/- 0.08 J m(-2) for SDRS and 0.85 +/- 0.20 J m(-2) for GISAXS). This demonstrates that the very flexible laboratory SDRS can be used to study the growth of a film in a similar way as the well-documented small angle x-ray scattering provided it is analyzed in an appropriate framework.