Characterization of the interface of gold and silver nanostructures on InP and GaAs synthesized via galvanic displacement

This work describes an investigation of the nature of the interface formed between the metals gold and silver, and the technologically relevant semiconductor substrates, InP and GaAs, produced via room temperature galvanic displacement. Immersion of these III-V semiconducting materials in a solution of the ionic gold and silver precursors results in deposition of firmly bound metal on the surface with varying morphologies, depending upon the conditions. Depth profile XPS indicates the presence of sandwiched intermetallic layers in the case of gold on GaAs and InP, but little evidence of a corresponding intermetallic with silver was observed. Cross section scanning Auger electron line profile spectra suggest little diffusion of the metals into the semiconductor lattice. It appears, therefore, that in the case of gold on InP and GaAs, dissociative diffusion of the semiconductor into the metal is favored, leading to a structure in which the intermetallic is located at an abrupt semiconductor-intermetallic boundary. The compositions of the gold intermetallics for GaAs and InP are most likely gamma-Au9Ga4 and AuGa for the first and AuIn and AuIn2 for the second, respectively.