Ultra-thin Au films with thickness (h) ranging from 0.5 to 6.0 nm were deposited at room temperature (RT) by means of e-beam evaporation on SiO 2 and HfO 2. Due to the natural solid-state dewetting (SSD) of the as-deposited films, Au nanoparticles (NPs) were formed on the substrates. By properly adjusting the h value, the size and the density of the Au NPs can be finely tuned. For h= 0.5 nm, spherical-like Au NPs with diameter below 5 nm and density in the order of 10 12 Au NPs cm− 2 were obtained without any additional thermal treatment independently from the substrate. The dependence of the Au NPs characteristics on the substrate starts to be effective for h≥ 1.0 nm where the Au NPs diameter is in the 5–10 nm range and the density is around 10 11 Au NPs cm− 2. The effect of a subsequent high temperature (400–800 C) annealing in N 2 atmosphere on the Au NPs was investigated as well. For h≤ 1.0 nm …