Electric field induced semiconductor-to-metal phase transition in vertical MoTe2 and Mo1-xWxTe2 devices

TL;DR

This paper demonstrates a reversible electric field-induced phase transition in ultrathin MoTe2 and Mo1-xWxTe2 devices, enabling electrical switching between semiconductor and metallic phases, with detailed nanoscale structural analysis and potential memory device applications.

Contribution

It reports the first experimental observation of electric field-induced reversible phase switching in vertical TMD devices, combining microscopy techniques to confirm phase changes and demonstrating tunable resistive memory behavior.

Findings

Reversible semiconductor-to-metal phase transition induced by electric field.

Structural confirmation of phase change via STM, STS, and STEM.

Demonstration of resistive memory devices with controllable switching voltages.

Abstract

Over the past years, transition metal dichalcogenides (TMDs) have attracted attention as potential building blocks for various electronic applications due to their atomically thin nature. An exciting development is the recent success in 'engineering' crystal phases of TMD compounds during the growth due to their polymorphic character. Here, we report an electric field induced reversible engineered phase transition in vertical 2H-MoTe2 devices, a crucial experimental finding that enables electrical phase switching for these ultra-thin layered materials. Scanning tunneling microscopy (STM) was utilized to analyze the TMD crystalline structure after applying an electric field, and scanning tunneling spectroscopy (STS) was employed to map a semiconductor-to-metal phase transition on the nanoscale. In addition, direct confirmation of a phase transition from 2H semiconductor to a distorted 2H' metallic phase was obtained by scanning transmission electron microscopy (STEM). MoTe2 and Mo1-xWxTe2 alloy based vertical resistive random access memory (RRAM) cells were fabricated to demonstrate clear reproducible and controlled switching with programming voltages that are tunable by the layer thickness and that show a distinctly different trend for the binary compound if compared to the ternary materials.