Tokyo Tech News

Terahertz technology: The potential of nano-carbon


February 28, 2013

The terahertz (THz, 1012Hz) frequency region is between the microwave and visible range of frequencies. Notably, THz technology is in strong demand in basic research in areas such as biochemical spectroscopy, astronomy, and materials science as well as applications including environmental science, medicine, agriculture, and security.

 These applications require highly sensitive detectors to obtain distinct THz spectra and images. In the THz region, however, even basic components like detectors and sources have not been fully established, compared to other frequency ranges that are technically mature.

Now, Yukio Kawano and colleagues at Tokyo Tech have developed novel types of THz devices based on nano-carbon materials: carbon nanotube (CNT) and graphene. 

A CNT single-electron transistor was integrated with a GaAs/AlGaAs heterostructure chip incorporating a two-dimensional electron gas (2DEG). A mono-layer graphene was exfoliated from graphite and attached onto the SiO2/Si chip. The researchers fabricated a graphene transistor with current electrodes made from Cr/Au and a back-gate electrode. 

Experimental results showed the CNT/2DEG hybrid device to be capable of detecting a small number of THz photons, while the graphene device enabled wide-band frequency-tunable THz and infrared detection. 

These new functional THz devices are expected to be used as powerful tools for THz spectroscopy and imaging. 

[1] Yukio Kawano, Terahertz Sensing and Imaging Based on Nanostructured Semiconductors and Carbon Materials, Laser & Photonics Reviews 6, 246 (2012).
[2] Yukio Kawano, Wide-Band Frequency-Tunable Terahertz and Infrared Detection with Graphene, Nanotechnology (2013). In press.
· Affiliations: Quantum Nanoelectronics Research Center, Department of Physical Electronics, Tokyo Institute of Technology.
· Department website:

CNT/2DEG hybrid THz detector