Limits...
Modeling of switching mechanism in GeSbTe chalcogenide superlattices.

Yu X, Robertson J - Sci Rep (2015)

Bottom Line: Model 2 proposes a switch between Petrov and Inverted Petrov states.For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure.Through calculating energy barriers, the rate-determining step is the displacive transition.

View Article: PubMed Central - PubMed

Affiliation: Engineering Dept, University of Cambridge, Cambridge CB2 1PZ, UK.

ABSTRACT
We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.

No MeSH data available.


Variation of enthalpy against temperature.The Ferro phase has the highest enthalpy at low temperature, but it gets more stable above 125K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4518231&req=5

f2: Variation of enthalpy against temperature.The Ferro phase has the highest enthalpy at low temperature, but it gets more stable above 125K.

Mentions: The relative stability of these four structures depends on temperature, which we have calculated from the phonon dispersion spectrum and plotted the enthalpy diagram against temperature in Fig. 2. From this, we see that the Kooi structure has the lowest enthalpy at 0 K, as previously found by Tominaga et al.6. However, the Kooi phase is unfavorable for switching. We see that by raising the temperature by 200 K, the enthalpy of the Kooi state increases and the Ferro structure becomes the more stable phase. This was a motivation to deposit the CSLs at ~250 °C, to favor the Ferro phase6.


Modeling of switching mechanism in GeSbTe chalcogenide superlattices.

Yu X, Robertson J - Sci Rep (2015)

Variation of enthalpy against temperature.The Ferro phase has the highest enthalpy at low temperature, but it gets more stable above 125K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4518231&req=5

f2: Variation of enthalpy against temperature.The Ferro phase has the highest enthalpy at low temperature, but it gets more stable above 125K.
Mentions: The relative stability of these four structures depends on temperature, which we have calculated from the phonon dispersion spectrum and plotted the enthalpy diagram against temperature in Fig. 2. From this, we see that the Kooi structure has the lowest enthalpy at 0 K, as previously found by Tominaga et al.6. However, the Kooi phase is unfavorable for switching. We see that by raising the temperature by 200 K, the enthalpy of the Kooi state increases and the Ferro structure becomes the more stable phase. This was a motivation to deposit the CSLs at ~250 °C, to favor the Ferro phase6.

Bottom Line: Model 2 proposes a switch between Petrov and Inverted Petrov states.For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure.Through calculating energy barriers, the rate-determining step is the displacive transition.

View Article: PubMed Central - PubMed

Affiliation: Engineering Dept, University of Cambridge, Cambridge CB2 1PZ, UK.

ABSTRACT
We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.

No MeSH data available.