An Integrated Tantalum Sulfide - Boron Nitride - Graphene Oscillator: A Charge-Density-Wave Device Operating at Room Temperature

TL;DR

This paper demonstrates a room-temperature oscillator based on a layered 2D charge-density-wave material, integrated with boron nitride and graphene, achieving a compact, voltage-controlled device with potential THz operation.

Contribution

It introduces a novel 2D material-based oscillator operating at room temperature, integrating TaS2, boron nitride, and graphene for tunable, miniaturized electronic applications.

Findings

Oscillator operates at room temperature with charge-density-wave transition.

Integration of 2D materials enables voltage-tunable frequency control.

Theoretical analysis suggests potential THz frequency operation.

Abstract

The charge-density-wave (CDW) phase is a macroscopic quantum state consisting of a periodic modulation of the electronic charge density accompanied by a periodic distortion of the atomic lattice in quasi-1D or layered 2D metallic crystals. Several layered transition metal dichalcogenides, such as 1T-TaSe2, 1T-TaS2 and 1T-TiSe2, exhibit unusually high transition temperatures to different CDW symmetry-reducing phases. These transitions can be affected by environmental conditions, film thickness and applied electric bias. However, device applications of these intriguing systems at room temperature or their integration with other 2D materials have not been explored. Here we show that in 2D CDW 1T-TaS2, the abrupt change in the electrical conductivity and hysteresis at the transition point between nearly-commensurate and incommensurate charge-density-wave phases can be used for constructing an oscillator that operates at room temperature. The hexagonal boron nitride was capped on 1T-TaS2 thin film to provide protection from oxidation, and an integrated graphene transistor provides a voltage tunable, matched, low-resistance load enabling precise voltage control of the oscillator frequency. The integration of these three disparate two-dimensional materials, in a way that exploits the unique properties of each, yields a simple, miniaturized, voltage-controlled oscillator device. Theoretical considerations suggest that the upper limit of oscillation frequency to be in the THz regime.