Growth and dewetting of gold on Si(1 1 1) investigated in situ by grazing incidence small angle x-ray scattering

The most accessible way to grow semiconductor nanowires remains so far the use of gold nanoclusters on a (1 1 1) semiconductor surface, for instance Si(1 1 1). Precise knowledge of the morphology of gold nanoparticles obtained by growth or dewetting on Si(1 1 1) is essential to better control the growth of nanowires. Both formation routes were investigated in situ by grazing incidence small-angle x-ray scattering. During the growth at 300 °C, Au atoms first nucleate on the wetting layer and give rise to islands having the shape of truncated spheres with an average contact angle of 38° for deposits of 1.4 and 2 monolayers. Dewetting is obtained by annealing of a 2 monolayer room temperature deposit, leading to the formation of particles. The average contact angle increases from 53° to 73° from 270 °C to 360 °C. Moreover, an analysis of the island height suggests that an AuSi alloy with a thickness of approximately 1.5 nm could be present at the top of the monocrystalline islands in the solid state before the eutectic temperature. The liquid–solid interface tension of the AuSi alloy droplet (1.0 J m−2) and the work of adhesion (1.1 J m−2) are deduced at the eutectic temperature.