Scanning Tunneling Microscopy of Au Nanoformations on Si (111) and Si (110) Surfaces

Using high-vacuum high-resolution scanning tunneling microscopy (STM) we have investigated the processes of hexagonal-pyramidal gold structures formation after thermal evaporation of gold onto monocrystalline Si (111) and Si (110) surfaces. It was found that under homogeneity of gold melt and vacuum not lower than 10⁻⁸ Pa there are formed self-ordered hexagonal-pyramidal nanostructures consisting of monoatomic layer planes each shifted by a distance of about 3 nm relatively to the growth start of the previous plane. The mechanism of formation of hexagonal-pyramidal gold nanostructures is determined with a character of electron density behaviour at the edge of each monoatomic layer. Extreme atoms of planes have higher energy state and thereby growth of each next monoatomic plane starts not from the edge but at the distance of about 3 nm from it what is caused with relaxation of inhomogeneity of electron density of states at this distance and determines pyramidal shape of formations. In the case of Si (110) plane there are observed only single-layered hexagonal formations. By other gold deposition modes there was observed formation of conglomerates of nanoparticles with subsequent transformation of them into ellipsoidal particles and further nanocrystal formation. The processes of gold nanoparticles agglomeration during thermal sputtering and after "wet" chemical synthesis are characterized with similar nanorelief pattern namely the formation of clusters of several nanoparticles.