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Carbon nanotube uncooled infrared image sensor

NEC Corporation recently announced that it has successfully developed the world's first high-sensitivity uncooled infrared image sensor using high-purity semiconductor carbon nanotubes (CNTs). The sensor uses NEC's proprietary semiconductor CNT extraction technology, and NEC plans to realize the practical application of this uncooled infrared image sensor in 2025.

Infrared image sensors convert infrared rays into electrical signals to obtain necessary information, so infrared rays emitted by people or objects can be detected even in the dark. At present, infrared image sensors have been widely used in various fields to provide safe and reliable social infrastructure, such as night vision systems that support driving in the dark, aircraft navigation support systems, and security cameras.

Infrared image sensors can be divided into two categories, one is the "cooled type" that operates at extremely low temperatures, and the other is the "uncooled type" that operates near room temperature. Cooled infrared image sensors have high sensitivity and responsiveness, but require coolers that are large in size, high in cost, high in power consumption, and regularly maintained. In contrast, uncooled infrared image sensors do not require a cooler, which makes them compact, economical, and low power consumption, but suffer from poor sensitivity and resolution compared to cooled types.

(Left) Electron micrograph and image of a single-walled CNT, (right) Atom microscope image of a high-purity semiconducting CNT film

NEC, which discovered CNT for the first time in the world in 1991, has become a leader in research and development in the field of nanotechnology. In 2018, NEC developed a proprietary technology capable of extracting high-purity semiconducting CNTs from mixed metal and semiconducting single-walled CNTs. NEC subsequently found that semiconducting CNT films extracted with this technique had a large temperature coefficient of resistance (TCR) near room temperature.

The newly developed infrared image sensor is based on the crystallization of these achievements and technologies. NEC has applied semiconductor CNT based on its proprietary technology, which is characterized by high TCR (an important indicator of high sensitivity). As a result, the new sensor is more than three times more sensitive than mainstream uncooled infrared image sensors using vanadium oxide or amorphous silicon.

(Left) Device structure, (Right) Photo of CNT infrared array device

Part of this work was done in collaboration with Japan's National Institute of Advanced Industrial Science and Technology (AIST). In addition, this work was supported by JPJ004596, a security technology research promotion program conducted by the Acquisition, Technology and Logistics Agency (ATLA) of the Ministry of Defense of Japan.

Going forward, NEC will continue to develop infrared image sensor technology to realize products and services that can contribute to various fields of society. Xinxin GEM provides infrared windows for infrared image sensor.

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