Reinforcing Band-to-Band Tunneling via Temperature Dependent Phase Transition in WS₂

Negative differential resistance (NDR) phenomenon is non-linear relationship that the current suddenly drops at a specific voltage range, showing a N-shaped current-voltage curve. The unique electrical property has been taken significant attention because of the potential applications in multi-logic devices, non-volatile memory, oscillator systems. Layered 2D materials is suitable to easily construct broken band alignment that is required to drive NDR performance such as boron nitride and black phosphorus. However, their unstable structure and additional processes to prevent degradation are still big challenges for improving the electron tunneling performance and feasibility. To overcome these limitations, we fabricated multiple-phased tungsten disulfide (MP-WS₂) thin film consisting of distorted 1T (D-1T) and 2H phase via plasma-assisted chemical vapor deposition (PECVD). As numerous ions in the plasma made high density of crystal seeds on the metal thin film, concomitant tensile stress led to the generation of multi-phases. It was possible that the outstanding stability and electric properties of D-1T phase attributed to long term endurance and high tunnelling efficiency. Additionally, the ratio of D-1T phase to 2H phase could be controlled with synthesis temperatures during the plasma treatment, resulting in the modification of NDR intensity. Finally, such phase engineering process during PECVD provides new insight for enhancing the sophisticated functionality of NDR devices.