In situ GISAXS study of gold film growth on conducting polymer films

The growth of a thin gold film on a conducting polymer surface from nucleation to formation of a continuous layer with a thickness of several nanometers is investigated in situ with grazing incidence small-angle X-ray scattering (GISAXS). Time resolution is achieved by performing the experiment in cycles of gold deposition on poly(N-vinylcarbazole) (PVK) and subsequently recording the GISAXS data. The 2D GISAXS patterns are simulated, and morphological parameters of the gold film on PVK such as the cluster size, shape, and correlation distance are extracted. For the quantitative description of the cluster size evolution, scaling laws are applied. The time evolution of the cluster morphology is explained with a growth model, suggesting a cluster growth proceeding in four steps, each dominated by a characteristic kinetic process: nucleation, lateral growth, coarsening, and vertical growth. A very limited amount of 6.5 wt % gold is observed to be incorporated inside a 1.2-nm-thick enrichment layer in the PVK film.