Chalcogenides alloy phases

Chalcogenide alloys such as GeSbTe-based compounds are of interest for applications in rewritable optical media (Digital Versatile Disc, Blu-ray disc) and in non-volatile electronic memory devices [1-5]. Both applications rest on a fast and reversible transformation between the crystalline and amorphous phases which represent the two states of the memory. The phase change is induced by heating, either... 

Phase change materials based on chalcogenide alloys are of widespread use in rewritable optical media (Digital Versatile Disc, Blu-ray disc) because of the strong optical contrast between the amorphous and crystalline phase (see inset of Fig. 15.9). Such a strong optical contrast is rather unusual since in typical semiconductors (e.g. GaAs in [91]) the amorphous and the crystalline phases have a similar... 

Perspectives for fabrication of improved oxygen electrodes at a low cost have been offered by non-noble, transition metal catalysts, although their intrinsic catalytic activity and stability are lower in comparison with those of Pt and Pt-alloys. The vast majority of these materials comprise (1) macrocyclic metal transition complexes of the N4-type having Fe or Co as the central metal ion, i.e., porphyrins, phthalocyanines, and tetraazaannulenes [6-8] (2) transition metal carbides, nitrides, and oxides (e.g., FeCjc, TaOjcNy, MnOx) and (3) transition metal chalcogenide cluster compounds based on Chevrel phases, and Ru-based cluster/amorphous systems that contain chalcogen elements, mostly selenium. 

Recently, we and others demonstrated that appropriate germanide Zintl clusters in non-aqueous liquid-crystalline phases of cationic surfactants can assemble well-ordered mesostructured and mesoporous germanium-based semiconductors. These include mesostructured cubic gyroidal and hexagonal mesoporous Ge as well as ordered mesoporous binary intermetallic alloys and Ge-rich chalcogenide semiconductors. 

The physicochemical properties of beryllium compounds and alloys have been reviewed subjects include phase diagrams, crystal structure, and density data on alloys and compounds, with a special section devoted entirely to halides and chalcogenides. ... 

With the sUver-chalcogenide clusters there is a tendency towards nonstoichiometry, as seen for the binary phases [76]. This behavior could be a consequence of the rather similar electronegativities of silver and the chalcogenides. There is no clear distinction between Ag" " and E (E = S, Se, Te), and the clusters behave rather like alloys [77]. 

Compared to the binary silver chalcogenide compounds, the phase transition temperature of monodisperse alloyed ternary silver chalcogenide Ag4SeS... 

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