Two-Dimensional Weyl Material-Based Negative Quantum Capacitance Effect for a Steep-Slope Hysteresis-Free Switching Device.

Abstract

The emergence of Weyl physics and associated materials offers promising pathways to circumvent the fundamental limitation imposed by Boltzmann tyranny, a thermionic constraint governing the subthreshold slope that currently prevents further reduction of operating voltages and overall power dissipation in field-effect transistors (FETs) and related devices. In this work, an ultrathin Weyl material, WTe₂, is utilized as a floating gate to achieve steep subthreshold (SS) hysteresis-free field-effect transistors based on the negative quantum capacitance (NQC) effect induced by the Weyl nodes. This device exhibits excellent performance in electrical characteristics, with a minimum SS of 20.3 mV/dec and an ultrasmall hysteresis of ∼2.6 mV. In addition, the optimal area ratio between WTe₂ and the channel (MoS₂) is found to be 1:1, and in this circumstance, a capacitance peak can be observed in the capacitance-voltage curve, suggesting the existence of the NQC effect. This effect is proposed to originate from the enhancement of the electron correlation effect as the Fermi level of WTe₂ is tuned to approach the Weyl nodes, which presents a low carrier density of state. This work benefits the design of high integration density, energy-saving devices and provides a possible method of optimizing traditional devices by introducing Weyl physics.