793 research outputs found
Disinflation, equity valuation, and investor rationality
An examination of the relationship between inflation and equity prices, concluding that equity prices respond rationally to such factors as real interest rates and risk.Corporations - Finance ; Inflation (Finance) ; Stocks
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Origin of resistivity contrast in interfacial phase-change memory: The crucial role of Ge/Sb intermixing
Phase-change memories based on reversible amorphous-crystal transformations in pseudobinary GeTe-Sb2Te3 alloys are one of the most promising nonvolatile memory technologies. The recently proposed superlattice-based memory, or interfacial phase-change memory (iPCM), is characterized by significantly faster switching, lower energy consumption, and better endurance. The switching mechanism in iPCM, where both the SET and RESET states are crystalline, is still contentious. Here, using the ab initio density functional theory simulations, a conceptually new switching mechanism for iPCM is derived, which is based on the change in the potential landscape of the bandgap, associated with local deviations from the pseudobinary stoichiometry across the van der Waals gaps and the associated shift of the Fermi level. The crucial role in this process belongs to Ge/Sb intermixing on the cation planes of iPCM. These findings offer a comprehensive understanding of the switching mechanisms in iPCM and are an essential step forward to the insightful development of phase-change memory technology.</jats:p
Ferroelectric switching in epitaxial GeTe films
In this paper, using a resonance-enhanced piezoresponse force microscopy approach
supported by density functional theory computer simulations, we have demonstrated
the ferroelectric switching in epitaxial GeTe films. It has been shown that in films with
thickness on the order of several nanometers reversible reorientation of polarization
occurs due to swapping of the shorter and longer Ge-Te bonds in the interior of the
material. It is also hinted that for ultra thin films consisting of just several atomic
layers weakly bonded to the substrate, ferroelectric switching may proceed through
exchange of Ge and Te planes within individual GeTe layers
A possible mechanism of ultrafast amorphization in phase-change memory alloys: an ion slingshot from the crystalline to amorphous position
We propose that the driving force of an ultrafast crystalline-to-amorphous
transition in phase-change memory alloys are strained bonds existing in the
(metastable) crystalline phase. For the prototypical example of GST, we
demonstrate that upon breaking of long Ge-Te bond by photoexcitation Ge ion
shot from an octahedral crystalline to a tetrahedral amorphous position by the
uncompensated force of strained short bonds. Subsequent lattice relaxation
stabilizes the tetrahedral surroundings of the Ge atoms and ensures the
long-term stability of the optically induced phase.Comment: 6 pages, 3 figure
Ferroelectric switching in epitaxial GeTe films
In this paper, using a resonance-enhanced piezoresponse force microscopy approach supported by density functional theory computer simulations, we have demonstrated the ferroelectric switching in epitaxial GeTe films. It has been shown that in films with thickness on the order of several nanometers reversible reorientation of polarization occurs due to swapping of the shorter and longer Ge-Te bonds in the interior of the material. It is also hinted that for ultra thin films consisting of just several atomic layers weakly bonded to the substrate, ferroelectric switching may proceed through exchange of Ge and Te planes within individual GeTe layers
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