Graduate students Kim Seong-jae and Jeon Yoon-chae from Professor Yu Ho-cheon's research team in the Department of Electronic Engineering have implemented a component that exhibits Negative Differential Resistance (NDR) when illuminated. This research has been published in the international academic journal Nano Letters (IF: 10.8) by the American Chemical Society. The paper is titled "Light-Triggerable and Gate-Tunable Negative Differential Resistance in Small Molecules Heterojunction."

The NDR characteristic involves a decrease in current as voltage increases, contrary to Ohm's law, where current increases with voltage. While this unique electrical property can be utilized in new applications such as multi-level logic circuits and frequency multipliers, previous NDR component research has faced difficulties in controlling NDR characteristics after fabrication, often remaining at the unit component level.

The research team induced photoresponsiveness to a broad range of light wavelengths by controlling the morphology of the materials used as channels. This allowed for light-triggered NDR characteristics and adjustable current levels of the NDR component based on the wavelength of light. Additionally, the proposed NDR component adopts a transistor structure, enabling the adjustment of the position of NDR characteristics even after fabrication using gate voltage. This means that NDR characteristics can be intentionally induced or eliminated within the same operating voltage range by adjusting the gate voltage.

Furthermore, Professor Yu Ho-cheon's team expanded their research to a 9 × 9 array scale composed of 81 NDR components at the unit component level. By observing NDR characteristics in all components comprising the NDR component array and verifying the uniformity and reproducibility of the proposed NDR component, they laid the foundation for future extension to application components.

Professor Yu stated, "The characteristic of Negative Differential Resistance, where current decreases as voltage increases, is intriguing on its own and can be expanded into new applications such as multi-level logic circuits and frequency multipliers." He added, "The significance of this research lies in the ability to control Negative Differential Resistance characteristics using light and gate voltage even after fabrication, which can be utilized in various fields such as logic circuits utilizing light signals."

This research was supported by the Korea Research Foundation and the Ministry of Trade, Industry and Energy. Professor Yu Ho-cheon's research team plans to continue additional research for the implementation of new applications based on Negative Differential Resistance components.

Link to the paper: https://pubs.acs.org/doi/10.1021/acs.nanolett.3c04671

Professor Yu Ho-cheon's research lab website: https://sites.google.com/view/sdclab/