Formation of the atomically smooth surface of gold film and binding of gold nano-particles on it by self-assembly method

Abstract

We have developed the technique of the surface's roughness decrease of gold films to atomic level. This technique consists of the accurate annealing of fresh-evaporated gold films by hot plate at temperature 250°C (or by free flame of gas-jet (T~700°C)). Films were evaporated thermally on atomically smooth mica substrates. The annealing of the gold film was carried out just after evaporation. The atomically smooth surface of gold film was obtained. The atomically smooth (roughness ~ 0.2 nm) regions have a sizes of 50-100 nm. It was found that the time from the end of evaporation process to the beginning of annealing process should be not more than 10 hours as well as a delay of the implementation of self-assembly process with annealed films and the analysis of results should be not more than 2 days. There was developed the method of gold nano-particles binding on the prepared by such way gold films. Evaporated and annealed gold film was treated by dithiol solution (1,2-ethanedithiol or 1,4-butanedithiol) with concentration of 0.05 g/mg and after that the samples were treated by the solution of gold nano-particles (2*10 -3 — 2.5*10 -5 mol/l). We have sorted out the optimal concentrations of gold nano-particles in various solvents, temperature and process duration which exclude the nano-particles' conglomeration and guarantee the uniform distribution of nanoparticles on film surface. The absence of nano-particles' conglutination was confirmed by the examination of samples with Scanning Tunneling Microscope and Scanning Electron Microscope. These examinations demonstrate the uniform distribution of small (3-13 nm) nano-particles on gold surface with the density of about 3 particles per 1000 nm 2 .