Carbon Nanotube Quantum Dot Terahertz Detectors and On-Chip High Resolution near-field terahertz detector

July 03, 2009

Carbon Nanotube Quantum Dot Terahertz Detectors and On-Chip High Resolution near-field terahertz detector

Posted by: admin : Category: Technology

Two types of emerging terahertz detectors are based on novel nanoelectronic technologies. Future work to combine the two will enable a real time terahertz video camera.

1. A highly sensitive and frequency tunable terahertz detector based on a carbon nanotube (CNT) quantum dot (QD).

<img style=" ) and a schematic representation (right) shows the design of a highly sensitive on-chip near-field THz detector. The 8-µm-diameter aperture and planar metallic probe, each of which is insulated by a 50-nm-thick silicon dioxide (SiO2) layer, are deposited on the surface of a GaAs/AlGaAs heterostructure chip. (Courtesy of RIKEN)

Because integration with the CNT-QD detector requires improvements in the device fabrication process (specifically, by using higher-performance electron-beam lithography equipment), a two-dimensional electron gas (2DEG)—located only 60 nm below the chip surface—is used as the terahertz detector.

Why Terahertz Detection is Tough

The photon energy of the terahertz wave, on the order of millielectron volts (meV), is two to three magnitudes lower than that of the visible light, making the development of a high-performance terahertz detector a difficult task. Another problem with terahertz detection is low spatial resolution of terahertz imaging, which results from the longer wavelengths of terahertz radiation compared to that of visible light.

Work to Combine the Carbon Nanotube Quantum Dot Detector for Near Field Detection

One of the challenges for future terahertz sensing technology is to achieve high detection sensitivity and high spatial resolution simultaneously. To realize this, we are now trying to combine the two techniques described above; namely to modify the CNT-QD terahertz detector into a similar structure for near-field detection. Compared to the 2DEG detector, the CNT detector exhibits much higher sensitivity and has a much smaller sensing area (approximately 200 nm compared to 8 µm for the 2DEG detector). This detector, integrated with an aperture and a probe, would show ultrahigh sensitivity and nanometer resolution simultaneously.

We further expect that when many CNTs are integrated in a two dimensional configuration, the resulting device will serve as a real-time, high-resolution terahertz imaging detector; in effect, a terahertz video camera.