Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge-V-Te (V = As, Sb) Liquid Alloys: The Difference One Element Can Make
AffiliationUniv Arizona, Dept Mat Sci & Engn
MetadataShow full item record
PublisherAMER PHYSICAL SOC
CitationGlass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge-V-Te (V = As, Sb) Liquid Alloys: The Difference One Element Can Make 2017, 7 (3) Physical Review Applied
JournalPhysical Review Applied
Rights© 2017 American Physical Society
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractGlass-transition temperatures (T-g) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of T-g vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e.,in the order S < Se < Te, the bond-density effect on T-g becomes systematically weaker, with a crossover at < r > = 2.3. When the more metallic Sb replaces As at < r > greater than 2.3, incipient metallicity rather than directional bond covalency apparently gains control of the physics. This observation leads us to an examination of the electronic conductivity and then semiconductor-to-metal (SC-M) transitions, with their associated thermodynamic manifestations in relevant liquid alloys. The thermodynamic components, as seen previously, control liquid fragility and cause fragile-to-strong transitions during cooling. We tentatively conclude that liquid-state behavior in phase-change materials is controlled by liquid-liquid (LL) and SC-M transitions that have become submerged below the liquidus surface. In the case of the Ge-Te binary, a crude extrapolation toGeTe stoichiometry indicates that the SC-Mtransition lies about20% belowthe melting point, suggesting a parallel with the intensely researched "hidden liquid-liquid transition" in supercooled water. In the water case, superfast crystallization initiates in the high-fragility domain some 4% above the LL transition temperature (T-LL) which is located at approximately 15% below the (ambient pressure) melting point.
VersionFinal published version
SponsorsNational Science Foundation [CHE-13265, ECCS-1201865]; Alexander von Humboldt Foundation Feodor Lynen Postdoctoral Research Fellowship