Surface patterning of GaAs under irradiation with very heavy polyatomic Au ions

Self-organization of surface patterns on GaAs under irradiation with heavy polyatomic Au ions has been observed. The patterns depend on the ion mass, and the substrate temperature as well as the incidence angle of the ions. At room temperature, under normal incidence the surface remains flat, whereas above 200 degree C nanodroplets of Ga appear after irradiation with monatomic, biatomic as well as triatomic Au ions of kinetic energies in the range of 10-30keV per atom. In the intermediate temperature range of 100-200 degree C meander- and dot-like patterns form, which are not related to Ga excess. Under oblique ion incidence up to 45 degree from the surface normal, at room temperature the surface remains flat for mon- and polyatomic Au ions. For bi- and triatomic ions in the range of 60 degree less than or equal to alpha less than or equal to 70 degree ripple patterns have been found, which become shingle-like for alpha greater than or equal to 80 degree , whereas the surface remains flat for monatomic ions.