Nanocarbon materials, such as carbon nanotubes and graphene, can potentially overcome the short comes in traditional
infrared detector materials because of their excellent electrical and optical properties such as adjustable electrical band
gap, low dark current, fast optical response time etc. This paper will present the development of an infrared imaging
system that is capable of infrared imaging without cooling. The sensing elements of the system are carbon nanotubes and
graphene. When they are illumined by an infrared light, the nano devices generate photocurrents, respectively. As a
result, infrared images can be presented based on using compressive sensing after the collection of photocurrent from the
nano devices. The development of this imaging system overcomes two major difficulties. First, the system uses singlepixel
nano photodetector, so the pixel crosstalk phenomena of conventional sensor arrays can be eliminated. Second, the
requirement of single-pixel unit reduces the manufacturing difficulties and costs. Under this compressive sensing camera
configuration, 50 × 50 pixel infrared images can be reconstructed efficiently. The results demonstrated a possible
solution to overcome the limitation of current infrared imaging.
Using carbon nanotubes (CNT), high performance infrared detectors have been developed. Since the CNTs have
extraordinary optoelectronics properties due to its unique one dimensional geometry and structure, the CNT
based infrared detectors have extremely low dark current, low noise equivalent temperature difference (NETD),
short response time, and high dynamic range. Most importantly, it can detect 3-5 um middle-wave infrared
(MWIR) at room temperature. This unique feature can significantly reduce the size and weight of a MWIR
imaging system by eliminating a cryogenic cooling system. However, there are two major difficulties that impede
the application of CNT based IR detectors for imaging systems. First, the small diameter of the CNTs results in
low fill factor. Secondly, it is difficult to fabricate large scale of detector array for high resolution focal plane due
to the limitations on the efficiency and cost of the manufacturing. In this paper, a new CNT based IR imaging
system will be presented. Integrating the CNT detectors with photonic crystal resonant cavity, the fill factor
of the CNT based IR sensor can reach as high as 0.91. Furthermore, using the compressive sensing technology,
a high resolution imaging can be achieved by CNT based IR detectors. The experimental testing results show
that the new imaging system can achieve the superb performance enabled by CNT based IR detectors, and, at
the same time, overcame its difficulties to achieve high resolution and efficient imaging.
Recently, scientists have been looking for novel materials to improve the performance of optoelectronic devices.
Graphene opens up new possibilities for infrared (IR) sensing applications. With a zero-bandgap graphene, electron-hole
pairs can be generated easily by low energy photons such as middle-wave infrared signal. We have used an electricfield-
assisted method to manipulate graphene between metal microelectrodes successfully. When a graphene contacts
with a metal, a built-in potential forms at the interface and it separates the electron-hole pairs that flow as photocurrents.
Based on this principle, we demonstrated using the graphene-based devices for infrared detection under a zero-bias
operation. We also tried to apply the devices with positive and negative bias voltages, and results indicated the flow of
photocurrent is independent of the polarity of the bias voltages.
Infrared (IR) detectors are enormously important for various applications including medical diagnosis, night vision etc.
The current bottleneck of high-sensitive IR detectors is the requirement of cryogenic cooling to reduce the noise. Carbon
nanotubes (CNTs) exhibit low dark current which allows CNTs to work without cooling. This paper presents the
development of noncryogenic cooled IR focal plane array (FPA) using CNTs. The FPA consists of an array of CNTbased
IR detectors which are sensitive to IR signal at room temperature. The CNT-based detectors can be made by our
nanomanufacturing process. And the sensitivity of the detectors at a special wavelength can be achieved by selecting and
controlling the bandgap of CNTs during the process. Besides, a readout circuitry has been integrated with the FPA to
retrieve signals from the detectors for high throughput applications.
We report high sensitivity carbon nanotube (CNT) based middle wave infrared (MWIR) sensors with a two-dimensional
photonic crystal waveguide. MWIR sensors are of great importance in a variety of current military applications including
ballistic missile defense, surveillance and target detection. Unlike other existing MWIR sensing materials, CNTs exhibit
low noise level and can be used as new nano sensing materials for MWIR detection where cryogenic cooling is not
required. However, the quantum efficiency of the CNT based infrared sensor is still limited by the small sensing area and
low incoming electric field. Here, a photonic nanostructure is used as a resonant cavity for boosting the electric field
intensity at the position of the CNT sensing element. A two-dimensional photonic crystal with periodic holes in a
polymer thin film is fabricated and a resonant cavity is formed by removing holes from the array of the photonic crystal.
Based on the design of the photonic crystal topologies, we theoretically study the electric field distribution to predict the
resonant behavior of the structure. Numerical simulations reveal the field is enhanced and almost fully confined to the
defect region of the photonic crystal. To verify the electric field enhancement effect, experiments are also performed to
measure the photocurrent response of the sensor with and without the photonic crystal resonant cavity. Experimental
results show that the photocurrent increases ~3 times after adding the photonic crystal resonant cavity.
KEYWORDS: Photodiodes, Signal detection, Staring arrays, Electrodes, Mid-IR, Infrared radiation, Semiconductors, Signal processing, Infrared detectors, Electron transport
This paper presents the development of non-cryogenic-cooling spectrum infrared (IR) focal plane array (FPA) using a
single carbon nanotube (CNT). The FPA consists of an array of CNT-based photodiodes. The CNT-based photodiodes
can be made by our nanomanufacturing process and band gaps of CNTs can be tuned precisely by the electric
breakdown system. As a result, the CNT-based photodiodes with high sensitivity at a special wavelength can be
achieved. In this paper, design, fabrication and experimental results of the CNT-based IR photodiode are reported. The
results indicate that CNTs are very sensitive of middle-wave IR (MWIR) signal at room temperature. Moreover, the performances of the photodiodes have been evaluated. These results suggest that CNTs can be used in high throughput sensing applications.
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 has developed non cryogenic cool and multiple spectrums optical
sensors using single CNT and demonstrated the good sensitivity of CNT to the infrared light in different ranges. In this
paper, design, fabrication and experimental result of the CNT-based optical sensor were described. The results indicated
the band gap of CNTs can be tuned by electrical breakdown process, resulting multiple spectrum sensors can be
developed by controlling the band gap of CNTs. Moreover, the
CNT-based optical sensor detected the near-IR (NIR)
signal and middle-wave IR (MWIR) signal in room temperature environment, the temperature dependency of the sensors
has been studied.
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.
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