Realization of a reversible switching in TaO2 polymorphs via Peierls distortion for resistance random access memory

TL;DR

This paper predicts a new TaO2 structure that can reversibly switch between metallic and semiconducting phases via a low-energy Peierls distortion, offering a promising mechanism for resistance memory devices.

Contribution

It introduces a new triclinic TaO2 structure with a reversible phase transition mechanism suitable for RRAM applications, based on first-principles calculations.

Findings

T-TaO2 is a semiconductor with a 1.0 eV band gap.

R-TaO2 is a metallic conductor.

The phase transition energy barrier is low, at 0.19 and 0.23 eV/atom.

Abstract

Transition-metal-oxide based resistance random access memory is a promising candidate for next-generation universal non-volatile memories. Searching and designing appropriate new materials used in the memories becomes an urgent task. Here, a new structure with the TaO2 formula was predicted using evolutionary algorithms in combination with first-principles calculations. This new structure having a triclinic symmetry (T-TaO2) is both energetically and dynamically more favorable than the commonly believed rutile structure (R-TaO2). Our hybrid functional calculations show that T-TaO2 is a semiconductor with a band gap of 1.0 eV, while R-TaO2 is a metallic conductor. This large difference in electrical property makes TaO2 a potential candidate for resistance random access memory (RRAM). Furthermore, we have shown that T-TaO2 is actually a Peierls distorted R-TaO2 phase and the transition between these two structures is via a directional displacement of Ta atoms. The energy barrier for the reversible phase transition from R-TaO2 to T-TaO2 is 0.19 eV/atom and the other way around is 0.23 eV/atom, suggesting low power consumption for the resistance switch. The present findings provide a new mechanism for the resistance switch and will also stimulate experimental work to fabricate tantalum oxides based RRAM.