Memristive phase switching in two-dimensional crystals

TL;DR

This paper demonstrates memristive phase switching in nano-thick 2D crystals of 1T-TaS2, revealing slow kinetics, metastable states, and multi-step non-volatile memory behavior enabled by reduced thickness.

Contribution

It reports the first observation of memristive phase switching in 2D correlated electron crystals, highlighting the role of thickness reduction in enabling non-volatile electrical switching.

Findings

Memristive switching observed in nano-thick 1T-TaS2 crystals.

Thinning causes slow phase transition kinetics and metastable states.

Multi-step non-volatile memory states achieved via in-plane electric field.

Abstract

Scaling down materials to an atomic-layer level produces rich physical and chemical properties as exemplified in various two-dimensional (2D) crystals extending from graphene, transition metal dichalcogenides to black phosphorous. This is caused by the dramatic modification of electronic band structures. In such reduced dimensions, the electron correlation effects are also expected to be significantly changed from bulk systems. However, there are few attempts to realize novel phenomena in correlated 2D crystals. Here, we report memristive phase switching in nano-thick crystals of 1T-type tantalum disulfide (1T-TaS2), a first-order phase transition system. The ordering kinetics of the phase transition was revealed to become extremely slow as the thickness is reduced, resulting in an emergence of metastable states. Furthermore, we realized the unprecedented memristive switching to multi-step non-volatile states by applying in-plane electric field. The reduction of thickness is essential to achieve such non-volatile electrical switching behavior. The thinning-induced slow kinetics possibly makes the various metastable states robust and consequently realizes the non-volatile memory operation. The present result indicates that 2D crystal with correlated electrons is a novel nano-system to explore and functionalize multiple metastable states which are inaccessible in its bulk form.