Limits...
Relation between bandgap and resistance drift in amorphous phase change materials.

Rütten M, Kaes M, Albert A, Wuttig M, Salinga M - Sci Rep (2015)

Bottom Line: A widening of the bandgap upon annealing accompanied by a decrease of the optical dielectric constant ε∞ is observed for all three materials.Quantitative comparison with experimental data for the apparent activation energy of conduction reveals that the temporal evolution of bandgap and activation energy can be decoupled.The case of Ag4In3Sb67Te26, where the increase of activation energy is significantly smaller than the bandgap widening, demonstrates the possibility to identify new phase change materials with reduced resistance drift.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.

ABSTRACT
Memory based on phase change materials is currently the most promising candidate for bridging the gap in access time between memory and storage in traditional memory hierarchy. However, multilevel storage is still hindered by the so-called resistance drift commonly related to structural relaxation of the amorphous phase. Here, we present the temporal evolution of infrared spectra measured on amorphous thin films of the three phase change materials Ag4In3Sb67Te26, GeTe and the most popular Ge2Sb2Te5. A widening of the bandgap upon annealing accompanied by a decrease of the optical dielectric constant ε∞ is observed for all three materials. Quantitative comparison with experimental data for the apparent activation energy of conduction reveals that the temporal evolution of bandgap and activation energy can be decoupled. The case of Ag4In3Sb67Te26, where the increase of activation energy is significantly smaller than the bandgap widening, demonstrates the possibility to identify new phase change materials with reduced resistance drift.

No MeSH data available.


Related in: MedlinePlus

Left: Temperature dependence of  before (squares) and after annealing (dots). Right: Decrease of  during the intermediate annealing at 353 K for 27 hours. Materials are colour-coded as indicated in the legend. The starting values of  at 353 K are 23.7 (Ag4In3Sb67Te26), 17.0 (Ge2Sb2Te5) and 11.9 (GeTe) respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664898&req=5

f2: Left: Temperature dependence of before (squares) and after annealing (dots). Right: Decrease of during the intermediate annealing at 353 K for 27 hours. Materials are colour-coded as indicated in the legend. The starting values of at 353 K are 23.7 (Ag4In3Sb67Te26), 17.0 (Ge2Sb2Te5) and 11.9 (GeTe) respectively.

Mentions: After transferring the infrared spectra to the dielectric function of the studied phase change materials, we are now able to investigate the evolution of the optical properties upon annealing and cooling in detail. We start with extracting the optical dielectric constant from the low energy limit of for all three materials for annealing and cooling (see Fig. 2). Looking at the temporal evolution during annealing, the observed total decrease ranges from 1.2% (GST) to 1.8% (AIST) and 2.1% (GeTe). The measured decrease is small, but still not concealed by noise and it can be described by a law. The temperature dependence of is obtained before and after annealing, the latter causing a shift towards lower values for all three materials. Cooling from 353 K to 10 K decreases by 6.8% (GST), 10.7% (AIST) and 5.6% (GeTe).


Relation between bandgap and resistance drift in amorphous phase change materials.

Rütten M, Kaes M, Albert A, Wuttig M, Salinga M - Sci Rep (2015)

Left: Temperature dependence of  before (squares) and after annealing (dots). Right: Decrease of  during the intermediate annealing at 353 K for 27 hours. Materials are colour-coded as indicated in the legend. The starting values of  at 353 K are 23.7 (Ag4In3Sb67Te26), 17.0 (Ge2Sb2Te5) and 11.9 (GeTe) respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664898&req=5

f2: Left: Temperature dependence of before (squares) and after annealing (dots). Right: Decrease of during the intermediate annealing at 353 K for 27 hours. Materials are colour-coded as indicated in the legend. The starting values of at 353 K are 23.7 (Ag4In3Sb67Te26), 17.0 (Ge2Sb2Te5) and 11.9 (GeTe) respectively.
Mentions: After transferring the infrared spectra to the dielectric function of the studied phase change materials, we are now able to investigate the evolution of the optical properties upon annealing and cooling in detail. We start with extracting the optical dielectric constant from the low energy limit of for all three materials for annealing and cooling (see Fig. 2). Looking at the temporal evolution during annealing, the observed total decrease ranges from 1.2% (GST) to 1.8% (AIST) and 2.1% (GeTe). The measured decrease is small, but still not concealed by noise and it can be described by a law. The temperature dependence of is obtained before and after annealing, the latter causing a shift towards lower values for all three materials. Cooling from 353 K to 10 K decreases by 6.8% (GST), 10.7% (AIST) and 5.6% (GeTe).

Bottom Line: A widening of the bandgap upon annealing accompanied by a decrease of the optical dielectric constant ε∞ is observed for all three materials.Quantitative comparison with experimental data for the apparent activation energy of conduction reveals that the temporal evolution of bandgap and activation energy can be decoupled.The case of Ag4In3Sb67Te26, where the increase of activation energy is significantly smaller than the bandgap widening, demonstrates the possibility to identify new phase change materials with reduced resistance drift.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.

ABSTRACT
Memory based on phase change materials is currently the most promising candidate for bridging the gap in access time between memory and storage in traditional memory hierarchy. However, multilevel storage is still hindered by the so-called resistance drift commonly related to structural relaxation of the amorphous phase. Here, we present the temporal evolution of infrared spectra measured on amorphous thin films of the three phase change materials Ag4In3Sb67Te26, GeTe and the most popular Ge2Sb2Te5. A widening of the bandgap upon annealing accompanied by a decrease of the optical dielectric constant ε∞ is observed for all three materials. Quantitative comparison with experimental data for the apparent activation energy of conduction reveals that the temporal evolution of bandgap and activation energy can be decoupled. The case of Ag4In3Sb67Te26, where the increase of activation energy is significantly smaller than the bandgap widening, demonstrates the possibility to identify new phase change materials with reduced resistance drift.

No MeSH data available.


Related in: MedlinePlus