Faceting and defaceting phase transitions of Pd W (111)

Yu Wen Liao, L. H. Chen, K. C. Kao, C. H. Nien, Minn Tsong Lin, Ker Jar Song

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We have studied the faceting and defaceting phase transitions of Pd W (111). In apparent agreement with results of recent theoretical simulation, 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 after long annealing time while there is more than enough Pd remaining to induce faceting of the whole surface. This leads us to the proposal that 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. Such desorption loss could be effectively replenished via surface diffusion at the vicinity of the Pd 3d islands. The observed independence of the defaceting transition path on the heating rate is rationalized as the consequence of a balance in between the loss and the supply of Pd, which can establish very quickly as the temperature rises.

Original languageEnglish
Article number125428
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number12
StatePublished - 27 Mar 2007


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