Structural semiconductor-to-semimetal phase transition in two-dimensional materials induced by electrostatic gating

Abstract

Dynamic control of conductivity and optical properties via atomic structure changes is of technological importance in information storage. Energy consumption considerations provide a driving force towards employing thin materials in devices. Monolayer transition metal dichalcogenides are nearly atomically thin materials that can exist in multiple crystal structures, each with distinct electrical properties. By developing new density functional-based methods, we discover that electrostatic gating device configurations have the potential to drive structural semiconductor-to-semimetal phase transitions in some monolayer transition metal dichalcogenides. Here we show that the semiconductor-to-semimetal phase transition in monolayer MoTe2 can be driven by a gate voltage of several volts with appropriate choice of dielectric. We find that the transition gate voltage can be reduced arbitrarily by alloying, for example, for MoxW1−xTe2 monolayers. Our findings identify a new physical mechanism, not existing in bulk materials, to dynamically control structural phase transitions in two-dimensional materials, enabling potential applications in phase-change electronic devices.

Engineering the Structural and Electronic Phases of MoTe2 through W Substitution

“…The T d−phase is predicted to possess unique topological properties [6][7][8][9] which might lead to topologically protected non-dissipative transport channels 9 . Recently, it was argued that it is possible to locally induce phasetransformations in TMDs 3,10,11,14 , through chemical doping 12 , local heating 13 , or electric-field 14,15 to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements 11 . The combination of semiconducting and topological elements based upon the same compound, might produce a new generation of high performance, low dissipation optoelectronic elements.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…In recent years, MoTe2 has attracted much attention due to multiphase transition, [70][71][72][73] Weyl semimetal, [30] giant negative magnetoresistance and superconductivity. Doping is an efficient way to turn those properties.…”

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

“…The switching between these two different phases can be achieved through electrostatic gating, allowing excess charge to enter or leave the monolayer. 17 Note that the transition is driven by the addition or removal of charge from the material rather than the electric field associated with gating, i.e., a charge neutral monolayer in an applied field will not necessarily exhibit the effect. This mechanism is fundamentally distinct from thermally driven phase transitions.…”

“…Our recent theoretical work suggests that a structural phase transition can be driven in specific monolayer materials through electrostatic gating, 17 including monolayer MoTe 2 and potentially TaSe 2 . This transition has been reported to occur in subsequent experiments employing ionic liquids to achieve the requisite charge densities.…”

“…16,18 RESULTS Phase diagram of monolayer MoTe 2 under electrostatic gating Using the DFT-based approach developed in ref. 17 , we compute the voltage-excess charge phase diagram of monolayer MoTe 2 under electrostatic gating. This DFT-based approach models the parallel plate capacitor structure shown in Fig.…”