An investigation was made of the interface behavior between thiol-stabilized Au nanoparticle deposits and Cu, Ni or Ag. Instead of sintering or agglomeration, curing at 300C resulted in entire or partial melting of the deposited suspension. This was because of the markedly lower melting-point of the Au nanoparticles due to the size-effect. The melting point was measured to be 230 to 270C. Thus, a liquid-solid reaction could occur, between nanoparticle Au deposits and substrates, during the heating process. The elemental depth-profiles, as examined using X-ray photo-electron spectroscopy, demonstrated that stoichiometric intermetallic phases, probably Cu3Au and NiAu3, existed at the Au/Cu and Au/Ni interfaces, respectively, while a miscible solid solution of non-stoichiometric layer was found to have emerged at the Au/Ag interface. The chemical shifts of binding energies found at the reaction layers also reflected the alloying behavior at those interfaces.

Interdiffusion Behavior at the Interfaces between Deposits of Au Nanoparticles and Electronic Substrates. T.H.Kao, J.M.Song, I.G.Chen, T.Y.Dong, W.S.Hwang: Nanotechnology, 2007, 18[43], 435708 (8pp)