Thermal disordering of the Pt(110)-(1×2) surface

The temperature dependence of the structure of the clean, (1×{}2) reconstructed Pt(110) surface has been investigated by thermal-energy helium-atom scattering and low-energy electron diffraction. Two distinct phase transitions were observed: At about 1025 K a two-dimensional Isinglike transition from the well-ordered (1×{}2) missing-row reconstructed surface to a disordered but flat surface takes place, followed at about 1095 K by a Kosterlitz-Thouless transition into a rough phase. The measurements provide strong evidence for the phase in the intermediate-temperature regime being a flat phase like the disordered flat phase recently proposed by den Nijs. The precise microscopic structure of this intermediate phase, however, could not be quantified in detail.