Phase transitions at Al and Au surfaces: Deconstruction, roughening and premelting

A short outline of structural phase transitions at surfaces and their experimental verification will be given as an introduction, which will be followed by a review of experimental and theoretical results for Al and Au surfaces. We have studied Au(111)‐, Au(110)‐ and Au(100)‐surfaces by medium energy ion scattering (MEIS) experiments and Au(110)‐ as well as Al(110)‐surfaces by low energy electron diffraction (LEED) experiments. At the Au(110) (2×1)‐surface deconstruction is accompanied by the disappearance of monoatomic steps. At about 40 K above the deconstruction temperature roughening sets in. The rough surface begins to smoothen if due to the increasing diffusion the outermost layers start to transform into a quasi‐liquid state. The growth of the quasi‐liquid layer with increasing temperature follows a logarithmic law. Preroughening, roughening and premelting transitions have been detected at the Al(110)‐surface. Open questions regarding these phase transitions will be discussed.