Real Space Investigation of the Roughening and Deconstruction Transitions of Au(110)

As established by diffraction techniques Au(110)- (1×2), which is missing-row reconstructed at 300 K, consecutively undergoes two phase transitions upon heating: an Ising transition at ≈650K and a 3D roughening transition at ≈700K. Our teal space investigation with atomic scale resolution by temperature-variable scanning tunneling microscopy reveals that---contrary to present theoretical models---the Ising transition is due to antiphase domains developing during the 2D roughening of (1×3) steps. The missing-row configuration of interior terrace regions remains completely stable until the 3D roughening temperature, thus ruling out an order-disorder transition via lattice gas formation.