Origin of the off state variability in ReRAM cells

Iulia Salaoru, Ali Khiat, Qingjiang Li, Radu Berdan, Christos Papavassiliou, Themistoklis Prodromakis

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

This work exploits the switching dynamics of nanoscale resistive random access memory (ReRAM) cells with particular emphasis on the origin of the observed variability when cells are consecutively cycled/programmed at distinct memory states. It is demonstrated that this variance is a common feature of all ReRAM elements and is ascribed to the formation and rupture of conductive filaments that expand across the active core, independently of the material employed as the active switching core, the causal physical switching mechanism, the switching mode (bipolar/unipolar) or even the unit cells' dimensions. Our hypothesis is supported through both experimental and theoretical studies on TiO2 and In2O3 : SnO2 (ITO) based ReRAM cells programmed at three distinct resistive states. Our prototypes employed TiO2 or ITO active cores over 5 × 5 m2 and 100 × 100 m2 cell areas, with all tested devices demonstrating both unipolar and bipolar switching modalities. In the case of TiO 2-based cells, the underlying switching mechanism is based on the non-uniform displacement of ionic species that foster the formation of conductive filaments. On the other hand, the resistive switching observed in the ITO-based devices is considered to be due to a phase change mechanism. The selected experimental parameters allowed us to demonstrate that the observed programming variance is a common feature of all ReRAM devices, proving that its origin is dependent upon randomly oriented local disorders within the active core that have a substantial impact on the overall state variance, particularly for high-resistive states.

Original languageEnglish
Article number145102
JournalJournal of Physics D: Applied Physics
Volume47
Issue number14
DOIs
Publication statusPublished - 20 Mar 2014

Keywords / Materials (for Non-textual outputs)

  • bipolar
  • ReRAM
  • resistive switching
  • unipolar
  • variability

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