Thermal faceting behavior of Au(4,5,5)

The reversible Au(4,5,5) surface structure transformation has been followed by grazing incidence X-ray diffraction between 300 and 1000 K. At 300 K, t he hill-and-valley morphology obtained after sputtering and annealing at a temperature above 800 K has been found to be in remarkable agreement with l ow energy electron diffraction and scanning tunneling microscopy studies. I t consists of two orientational phases which are both Au(1,1,1) vicinal sur faces: the 4 degrees-phase which is reconstructed and the non-reconstructed 10 degrees-phase, The 4 degrees-phase presents a periodicity of 79 Angstro m, and the lines of discommensurations are perpendicular to the step edges. This result is consistent with the known interaction on the close-packed A u(111) surface between the reconstruction and the step edge atomic structur es. The temperature dependence of the faceted morphology is found to be rev ersible and independent of the cooling rate, Between 550 and 1000 K, the 4 degrees-phase continuously increases its angle of misorientation and it is still reconstructed. On the other hand, the 10 degrees phase structure does not change its angle of misorientation within the temperature range, but d ecreases in intensity. (C) 1999 Elsevier Science B.V. All rights reserved.