Sample Preparation and Surface Evolution

Over the years, several general reviews have been written about the surface science of QCs and approximants [36-40], and two entire journal volumes were devoted to collections of specialized reviews by prominent authors in the field [41, 42]. The reader may find that these sources offer perspectives that are different than, or complementary to, those discussed here. 

System Element(s) removed preferentially Atomic weights, in increasing order References 

At intermediate temperatures, one usually obtains a surface that is bulk-terminated, or is related to a bulk termination. This can be taken as the equilibrium structure, if equilibration is heuristically defined as the asymptotic limit of the surface state as a function of progressive annealing temperature/time, up to 

The dynamics by which QC surfaces reach equilibrium is very complex. There is evidence that several phenomena occur that have not been discussed for crystaUine surface evolution, to the authors knowledge. These include migration and condensation of bulk vacancies at surfaces [64-67], progressive step bunching [68, 69], and formation of metastable QC terraces [70-72]. 

Because of the chemical and structural damage inherent in sputter annealing, alternative approaches have been investigated. One is to transfer a sample from air to UHV, then heat it to sublime the surface oxide. Little work has been done to characterize surfaces produced by this method, except that STM images reveal faceted voids that may reflect metal evaporation [74]. Another approach is to fracture the sample [64-67,75-78]. This approach clearly causes the least chemical damage, but it may produce a nonequihbrium structure. An even larger problem is that fracture consumes samples irreversibly. 

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