Researchers uncover new properties in 2D semiconductor

Researchers from the National University of Singapore (NUS) have reported new findings on the properties of two-dimensional (2D) molybdenum disulfide (MoS₂), a widely studied semiconductor of the future.

In two separate studies led by Andrew Wee and Andrivo Rusydi from the Department of Physics at the NUS Faculty of Science, the researchers uncovered the role of oxygen in MoS₂ and developed a novel technique for creating multiple tunable, inverted optical band gaps in the 2D material. These novel insights provide greater understanding of the intrinsic properties of MoS₂, potentially transforming its applications in the semiconductor industry.

MoS₂ is a semiconductor-like material with desirable electronic and optical properties for the development and enhancement of transistors, photodetectors and solar cells. “MoS₂ holds great industrial importance,” explained Wee. “With an atomically thin two-dimensional structure and the presence of a 1.8eV energy band gap, MoS₂ is a semiconductor that can offer broader applications than graphene, which lacks a band gap.”

In the first study, reported in a paper in Physical Review Letters, Wee, Rusydi and their colleagues at NUS conducted an in-depth analysis of MoS₂, which revealed that its energy storage capacity or dielectric function can be altered using oxygen.

The team observed that MoS₂ displayed a higher dielectric function when exposed to oxygen. This new finding sheds light on how the adsorption and desorption of oxygen by MoS₂ can be employed to modify its electronic and optical properties to suit different applications. The study also highlights the need for adequate consideration of extrinsic factors that may affect the properties of the material in future research.

“With an atomically thin two-dimensional structure and the presence of a 1.8eV energy band gap, molybdenum disulfide is a semiconductor that can offer broader applications than graphene, which lacks a band gap.”Andrew Wee, National University of Singapore

In the second study, reported in a paper in Nature Communications, Wee, Rusydi and their colleagues discovered that, whereas conventional semiconductors typically have only one optical band gap, electron doping of MoS₂ on gold can create two unusual optical band gaps in the material. In addition, the two optical bandgaps in MoS₂ are tunable via a straightforward annealing process. The researchers also identified that the tunable optical band gaps are induced by strong-charge lattice coupling as a result of the electron doping.

The findings from the two studies also provide insights into other materials that possess a similar structure to MoS₂.

“MoS₂ falls under a group of materials known as the two-dimensional transitional metal dihalcogenides (2D-TMDs), which are of great research interest because of their potential industrial applications. The new knowledge from our studies will assist us in unlocking the possibilities of 2D-TMD-based applications such as the fabrication of 2D-TMD-based field effect transistors,” said Rusydi.

The researchers will now conduct similar studies on other 2D-TMDs and explore different possibilities for generating new, valuable properties in 2D-TMDs that do not exist in nature.

This story is adapted from material from the National University of Singapore, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.