HE BEAM STUDY OF DECONSTRUCTION AND ROUGHENING OF AU(110)(1X2)

The deconstruction of the Au(110) surface, i.e., the (1 x 2) --> (1 x 1) phase transition, has been studied by He beam scattering. A critical temperature of 700 +/- 5 K is indicated by the temperature dependence of the half-integral diffraction intensities, and the incoherent elastic intensity. Above 700 K the peak width variation is consistent with Ising-like behaviour, where the main contribution to lateral disorder comes from domain walls. It is also demonstrated that the roughening temperature is substantially larger than the deconstruction temperature. The tails of the specular peak decay as a function of parallel momentum according to a power law with exponent - 1.55 +/- 0.1 at 723 K, indicating that the roughening temperature is higher.