Electronic structure and morphology of thin surface alloy layers formed by deposition of Sn on Au(111)

We demonstrate formation of thin AuSn and Au2Sn surface alloy layers at room and elevated substrate temperatures (T-s = 413-493 K), respectively by the deposition of Sn on Au(1 1 1) using core-level X-ray photoelectron spectroscopy and scanning tunneling microscopy. Low energy electron diffraction patterns show dif- ferent surface structures: p(3 x 3) R15 degrees at room temperature for AuSn, [GRAPHICS] at T-s = 413 K and (root 3 x root 3) R30 degrees at T-s = 493 K for Au2Sn. Angle resolved photoemission spectroscopy reveals evolution of bands from an electron-like surface state to appearance of a hole-like band structure corresponding to AuSn and Au2Sn. The [GRAPHICS] phase of Au2Sn, which has a unit cell of oblique symmetry, exhibits an interesting linear band that meets at the Fermi level in the zone-center and have Fermi velocity comparable to graphene. Thus, our study establishes that Au-Sn bimetallic surface alloys have interesting electronic properties with potential for future applications.