Microstructural evolution in nanostructured gold films

Thin Au films in the thickness range t = 1.5–126 nm were coated by DC sputtering on SiOx/Si substrates at room temperature inside a vacuum chamber with a base pressure of about 1 × 10− 2 mbar (1 Pa). The film structure, nanograin characteristics, and the surface roughness as a function of thickness were analyzed using X-ray diffraction, scanning tunneling microscopy and transmission electron microscopy. The results reflect the microstructural evolution with film thickness. They help us to understand the mode of grain growth, which is monomodal-normal columnar as well as spherical. By determination of the dynamic scaling exponent derived from power law dependence of the mean grain size and film thickness, the prevailed mechanism of grain growth is deduced to be the diffusion of mobile Au atoms in grain boundaries. The surface roughness increases with the film thickness following a power law: Rrms ~ tb. The linear fitted value for b is 0.60.

► Au/SiOx/Si thin films were grown by DC sputtering in relatively low vacuum conditions.
► Au film grows by growth of normal spherical and columnar grains.
► The mean grain size, dg, and sample thickness, t, follow the power low: dg~t0.41.
► The roughness increases with film thickness following a power law: Rrms~t0.60.