  We have investigated the temperature-dependent morphology and composition
changes occurring during a controlled self-assembling of thin Au film on the
Gallium arsenide (001) surface utilizing electron microscopy at nano and atomic
levels. It has been found that the deposition of 2 ML of Au at a substrate
temperature lower than 798 K leads to the formation of pure Au nanoislands. For
the deposition at a substrate temperature of about 798 K the nanostructures of
the stoichiometric AuGa phase were/had been grown. Gold deposition at higher
substrate temperatures results in the formation of octagonal nanostructures
composed of an AuGa2 alloy. We have proved that the temperature-controlled
efficiency of Au-induced etching-like of the GaAs substrate follows in a
layer-by-layer manner leading to the enrichment of the substrate surface in
gallium. The excess Ga together with Au forms liquid droplets which, while
cooling the sample to room temperature, crystallize therein developing
crystalline nanostructures of atomically-sharp interfaces with the substrate.
The minimal stable cluster of 3 atoms and the activation energy for the surface
diffusion Ed=0.816+-0.038eV was determined. We show that by changing the
temperature of the self-assembling process one can control the phase, interface
and the size of the nanostructures formed.
