In the future, thermal imaging cameras like those used at airports could be made of tungsten and hafnium disulfide, materials that enable them to function efficiently at room temperature or higher.

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Paving the way for infrared photodetectors

14 Oct 2020

Faster temperature scanners may be on the way thanks to A*STAR researchers who have developed an infrared photodetector that works at room temperature.

With the need to control the potential spread of COVID-19, thermometers and temperature scanners have become a common sight at the entrance points to nearly all public spaces. In areas of high foot traffic such as in airports, where many people need to be screened in a short amount of time, scanners that operate on an infrared photodetector can get the job done quickly.

However, there’s a problem. While fast, most high-performance infrared photodetectors can only work at low temperatures, requiring bulky and expensive cryogenic cooling systems—not an ideal situation for temperature scanners in public spaces. A photodetector that could operate without the need for a cooling system would result in a cheaper and more compact scanner, which would help in its widespread market adoption.

A discovery by a team led by scientists from A*STAR’s Institute of Materials Research and Engineering (IMRE) and Institute of High Performance Computing (IHPC) has now taken us a step closer to this ideal system. They demonstrate that infrared photodetection enabled by interlayer excitons (ILEs) generated between tungsten and hafnium disulfide (WS2/HfS2) can operate at and above room temperature, paving the way towards cheaper and more convenient infrared photodetectors.

“One of the bottlenecks for mid-far infrared technology is the lack of high-efficiency photodetectors operable at room temperature,” said corresponding author Jinghua Teng, a Principal Scientist at IMRE. “We have been trying to solve this issue by using ILEs in 2D heterostructures. We chose WS2/HfS2 after carefully studying and screening various options.”

According to Teng, the highly responsive photodetection that they observed is a result of the large oscillator strength of the ILEs in the WS2/HfS2 heterostructure, combined with its large exciton binding energy and unique band alignment.

“We postulate this is due to the sizable charge delocalization and ILE accumulation at the interface,” said Teng.

The team also showed that their WS2/HfS2-based photodetector is more responsive at long wavelength infrared than any other 2D material-based device.

“Our work points to a promising direction for the development of future mid-far infrared photodetectors and photoemitters,” said Teng. Moving forward, he hopes to explore the potential of this technology and develop it for use in real-world applications such as photodetector arrays and infrared cameras.

“Extending the operation wavelength to the far-infrared and terahertz range would be another interesting and impactful work,” he added.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE) and the Institute of High Performance Computing (IHPC).

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Lukman, S., Ding, L., Xu, L., Tao Y., Riis-Jensen A. C., et al. High oscillator strength interlayer excitons in two-dimensional heterostructures for mid-infrared photodetection. Nature Nanotechnology 15, 675–682 (2020). | article

About the Researcher

Jinghua Teng

Principal Scientist

Institute of Materials Research and Engineering
Dr. Jinghua Teng is a Principal Scientist in the Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore. He received his B. Sc. in Physics and M. Sc. in Optics from Nankai University, and Ph.D. in Optoelectronics from the National University of Singapore. His research interests include nano-optics and photonics, metamaterials and metasurfaces, 2D optoelectronics, THz technology, plasmonics and semiconductor materials and devices.

This article was made for A*STAR Research by Wildtype Media Group