XPEEM study of liquid Au-Si droplets on Si(111) near to the eutectic point

We have analyzed the surface of liquid Au-Si eutectic droplets with photoemission spectromicroscopy. The Si 2p core level of the droplets shifts 0.2 eV to lower kinetic energy with respect to the surrounding Au/Si(111)-6x6 phase. The integral intensity of the Si 2p peak is approximately equal on the liquid droplet and on the surrounding substrate indicating that the local Au/Si stoichiometry does not change. Since bulk Au-Si liquid is Au-rich, this indicates that the liquid surface has a higher Si content than the bulk. An additional shoulder in the Si 2p spectrum of the droplet develops at 1.3 eV lower kinetic energy.