Permanent Dipole Moment in a Quantum-Confined Two-Dimensional Metal Revealed by Electric Double Layer Gating.

The tunable optical properties of metals through size-dependent quantum effects have attracted attention due to synthesis of chemically stable, ultrathin, and two-dimensional metals. Gate tunability, from the reduced screening of low-dimensional metals, adds an additional route for control over optical properties. Here, two-dimensional (2D) Ga is synthesized via confinement heteroepitaxy and patterned into electric-double-layer (EDL) gated transistors.

Bistable Electrical Switching Using a Crown Ether-Based Monolayer Electrolyte on WSe Field-Effect Transistors with Various Salts.

Bistable electrical switching using a crown-ether-based electrolyte on WSe field-effect transistors (FETs) is measured for four salts: LiClO, NaClO, Ca(ClO), and LiCl. The solid-state monolayer electrolyte comprises cobalt crown ether phthalocyanine in which cations are solvated by 15-crown-5 ethers. The switching mechanism is the toggling of cations through the crown ether cavity in response to an applied field, creating low and high resistance states in the WSe channel.

Strain-Induced 2H to 1T' Phase Transition in Suspended MoTe Using Electric Double Layer Gating.

MoTe can be converted from the semiconducting (2H) phase to the semimetallic (1T') phase by several stimuli including heat, electrochemical doping, and strain. This type of phase transition, if reversible and gate-controlled, could be useful for low-power memory and logic. In this work, a gate-controlled and fully reversible 2H to 1T' phase transition is demonstrated via strain in few-layer suspended MoTe field effect transistors.

Impact of Large Gate Voltages and Ultrathin Polymer Electrolytes on Carrier Density in Electric-Double-Layer-Gated Two-Dimensional Crystal Transistors.

Electric-double-layer (EDL) gating can induce large capacitance densities (∼1-10 μF cm) in two-dimensional (2D) semiconductors; however, several properties of the electrolyte limit performance. One property is the electrochemical activity which limits the gate voltage () that can be applied and therefore the maximum extent to which carriers can be modulated. A second property is electrolyte thickness, which sets the response speed of the EDL gate and therefore the time scale over which the channel can be doped.