Carbon nanotube (CNT) has been found to be one of the promising materials for efficient detection and used in different
nanoelectronic devices due to its unique electrical properties. Recently, the applications of nanostructural material to
infrared (IR) sensors are considered. Our group developed a color detector using a single CNT and demonstrated the
good sensitivity of CNT to the infrared light in different ranges. In this report, the CNT bandgap engineering was
discussed. The design, fabrication and experimental result of the CNT based color detector were described. The results
indicated the heterogeneous electrode structure increased the signal-to-dark current ratio. Moreover, the CNT based color
detectors were capable to sense near-infrared signal and middle-infrared signal in room temperature environment.
By forming a Schottky barrier with the contact metal, a semiconducting CNT based Schottky photodiode is
formed at the CNT-metal contact. The photogenerated electron-hole pairs within the depletion region of the
Schottky barrier are separated by an external electrical field or the built-in field, producing a photocurrent. How
to efficiently read this photocurrent signal out is an essential problem for the photodetectors. Since a semiconducting
CNT normally forms a Schottky barrier at each CNT-electrode contact, two Schottky photodiodes are
reversely connected and their photocurrents will cancel each other, which makes it difficult to measure the overall
photocurrent. With different materials as the contact electrodes, the asymmetric structure enlarged the difference
between the two CNT-metal contacts. Hence the measurable photocurrent is also enlarged. Furthermore,
since the CNT Schottky barrier is determined by the metal work function and the Fermi level of the CNT, the
Schottky barrier is able to be adjusted by controlling the Fermi level of the CNT with a gate electrode. In this
way, the photocurrent can be optimized to a maximum value by varying the gate voltage. CNT based infrared
detectors with different structures were fabricated and tested. Experimental results showed that the asymmetric
structure and the gate controlled CNT based photodiode could significantly improve the performance of CNT
based infrared detectors.
Carbon nanotubes (CNTs) have a potential to be efficient infrared (IR) detection materials due to their unique
electronic properties. The ballistic electronic transport property makes the noise equivalent temperature difference
smaller compared to other semiconducting materials. In order to explore this potential application, CNT
based IR detectors are fabricated by depositing the CNTs on the substrate surface and then aligning them using
the Atomic Force Microscopy (AFM) based nanomanipulation system. Normally semicnoductive CNT forms a
Schottky barrier with the contact metal. The photogenerated electron-hole pairs within the Schottky barrier
are seperated by an external electric field or the built-in field, producing a photocurrent. This paper will focus
on the performance evaluation and analysis for the CNT based IR detectors. Experiments were carried out to
investigate the photoresponse of single carbon nanotube based IR detectors. Based on the experimental results,
the detectivity D* and the quantum efficiency are calculated and analyzed. The MWNT IR detector has a quantum
efficiency of 0.313, which is much larger than the reported values of SWNTs. And the SWNT IR detector
has a quantum efficiency of 0.01, which is consistent with the reported values. Both MWNT and SWNT show
a low detectivity. The analysis shows that the performance of CNT based IR detectors can be further improved
by using asymmetric contacts instead of symmetric contacts.
Carbon nanotubes (CNTs) have a potential to be efficient infrared (IR) detection material due to their unique
electronic properties. As a one-dimensional nano-structural material, the ballistic electronic transport property
makes the noise equivalent temperature difference smaller compared with other semi-conducting materials. In
order to verify this unique property, a single pixel CNT-based infrared photodetector is fabricated by depositing
the CNTs on the substrate surface and then aligning them to bridge the electrode gap using the atomic force
microscopy (AFM)-based nano-robotic system. The photon-generated electron-hole pairs within the carbon
nanotube are separated by an external electric field between the two electrodes. The separated carriers contribute
to the current flowing through the carbon nanotube and form the photocurrent. By monitoring the photocurrent,
the incident infrared can be detected and quantified. Experimental results show the good sensitivity of CNTs to
the infrared light.
As a one-dimensional nanostructural material, carbon nanotube (CNT) has been used to build different nanoelectronic
devices due to its unique electrical properties. In this paper, the infrared (IR) responses of individual
single-wall carbon nanotube (SWNT) and SWNT film are studied. A single-wall carbon nanotube is assembled
onto a pair of electrodes to form Schottky contacts. The photongenerated electron-hole pairs within the carbon
nanotube are seperated by an external electric field between the two electrodes. The separated carriers contribute
to the current flowing through the carbon nanotube and form photocurrent. By monitoring the photocurrent,
the incident infrared can be detected and quantitated. The single-wall carbon nanotube based infrared sensor
is designed and a series of efficient and reliable fabrication and assembly processes are developed for the sensor
fabrication. With an atomic force microscope based nanomanipulation system as the assembly tool, a single
carbon nanotube can be easily assembled onto the electrodes. Since the assembly process is controllable and
reliable, it becomes possible to fabricate an individual carbon nanotubes based infrared sensor array, which was
difficult to fabricate with other fabrication method. The photocurrent responses of individual SWNT IR sensor
and SWNT film IR sensor are measured and analyzed. Experimental results show the good sensitivity of SWNTs
to the infrared light. Our results shows a three orders higher photocurrent than the previous reported results.
It has also been shown that an individual SWNT IR sensor is more sensitive than a SWNT film IR sensor.
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