中央研究院 原子與分子科學研究所

We have studied the faceting and defaceting phase transitions of Pd/W(
111). In apparent agreement with results of recent theoretical simulation [C. Oleksy, Surf. Sci. 549, 246
(2004)], we find the fastest way to create the largest facets is to anneal at a temperature right below the temperature that the defaceting transition occurs. On the other hand, while the paths of faceting transitions show normal retardation as the cooling rate is increased, the paths of defaceting transitions show negligible dependence on the heating rate even if increased by 64-fold. Another notable observation is a phase separation of the surface into defaceted and faceted regions

We find the fastest way to create the largest facets is to anneal at 1130K, which is right below the defaceting transition temperature. One notable observation is a phase separation of the surface into defaceted and faceted regions after long time annealing at 1100K while there is more than enough Pd remaining to induce faceting of the whole surface. Instead of thermal disorder, the observed defaceting transition of the Pd/W(111) system is mainly driven by local loss of Pd, which is due to thermal desorption.