Thermal roughening restrained by bulk chemical order: Cu–Pd(17%)(1 1 5) versus Cu(1 1 5) and Cu3Au(1 1 12) surfaces

In contrast with dense surfaces, pure metal vicinal surfaces exhibit a roughening transition temperature well below their melting point. Although the surface structure of the single step Cu–Pd(17%)(1 1 5) and Cu(1 1 5) is similar, it is pointed out that the two surfaces have a very different behavior for thermal step disordering. If the roughening temperature of Cu(1 1 5) is found to be of 380 K, the alloy surface does not roughen up to the vicinity of the bulk chemical order–disorder transition (Tc=778 K). This result point out the interest of ordered alloys to produce high temperature stable flat surfaces.