title: Relation between bandgap and resistance drift in amorphous phase change materials.
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.
authors.affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.|IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Rütten
authors.affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kaes
authors.affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Albert
authors.affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wuttig
authors.affiliation: Institute of Physics 1A, RWTH Aachen University, Sommerfeldstrasse 14, 52074 Aachen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Salinga