Electric-field-induced annihilation of localized gap defect states in amorphous phase-change memory materials

Konstantinos Konstantinou, Felix C. Mocanu, Jaakko Akola, Stephen R. Elliott

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Structural relaxation of amorphous phase-change-memory materials has been attributed to defect-state annihilation from the band gap, leading to a time-dependent drift in the electrical resistance, which hinders the development of multi-level memory devices with increased data-storage density. In this computational study, homogeneous electric fields have been applied, by utilizing a Berry-phase approach with hybrid-density-functional-theory simulations, to ascertain their effect on the atomic and electronic structures associated with the mid-gap states in models of the prototypical glassy phase-change material, Ge2Sb2Te5. Above a threshold value, electric fields remove spatially localized defects from the band gap and transform them into delocalized conduction-band-edge electronic states. A lowering of the nearest-neighbor coordination of Ge atoms in the local environment of the defect-host motif is observed, accompanied by a breaking of 4-fold rings. This engineered structural relaxation, through electric-field tuning of electronic and geometric properties in the amorphous phase, paves the way to the design of optimized glasses.

Original languageEnglish
Article number117465
Number of pages11
JournalActa Materialia
Volume223
Early online date6 Nov 2021
DOIs
Publication statusPublished - 15 Jan 2022
Publication typeA1 Journal article-refereed

Keywords

  • Amorphous materials
  • Defects
  • Electric field
  • First-principles calculations
  • Phase-change memory

Publication forum classification

  • Publication forum level 3

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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